Physiology MCQs for NEET PG
951 worked Physiology questions across 90 areas. Each one has its own page with the reasoning for every option.
What this set is
Physiology rewards understanding mechanisms: why a value rises or falls when a variable changes. Graphs, flow charts and 'what happens if' reasoning matter more than recalling definitions.
This page lists the 951 Physiology questions that have a full worked page: 677 application questions that put a fact to use on a patient or a finding, and 274 multi-step questions that combine two or more ideas. Plain one-fact recall items are left out here on purpose. The Physiology practice bank in the app is larger, with 3,980 questions in all, and is where timed tests and daily practice draw from.
How to use it
- Pick an area you are weak in, below.
- Answer first, then read why each wrong option fails.
- Write a three-line note for every miss, and revisit it in a week.
- Move to a timed Physiology test once an area feels steady.
These are original practice items, not recalled exam questions, and they are not yet reviewed by independent faculty. Confirm important facts in a standard textbook.
What Physiology covers in the exam
- General physiology
- Blood and immunity
- Nerve and muscle
- Cardiovascular system
- Respiratory system
- Renal and acid–base
- Gastrointestinal
- Endocrinology
- Reproduction
- Neurophysiology and special senses
A study map from the standard curriculum; the NBEMS bulletin is the authority. See the Physiology study guide.
Worked questions by area
90 areas, largest first. Open an area to see its questions.
Respiratory system60
- Respiratory system: compliance in emphysema · ApplicationA 62-year-old smoker with emphysema has a barrel-shaped chest. Which change in lung mechanics best explains his hyperinflation?
- Respiratory system: spirometry interpretation · Multi-stepA 55-year-old man with progressive dyspnoea has FVC 52% of predicted, FEV1 50% of predicted and FEV1/FVC of 0.82. Which interpretation is correct?
- Respiratory system: helium dilution · Multi-stepIn a closed-circuit helium dilution test, a 4 L spirometer contains 8% helium. After the patient rebreathes from it at the end of a normal expiration, the helium concen…
- Respiratory system: airway resistance · ApplicationDuring an asthma attack, bronchial smooth muscle contraction halves the radius of a medium airway. Assuming laminar flow, by what factor does the resistance of that air…
- Respiratory system: dynamic airway compression · ApplicationA patient with COPD breathes out through pursed lips and feels less breathless. How does this help?
- Respiratory system: alveolar-arterial gradient · Multi-stepA 25-year-old man is found drowsy with slow, shallow breathing after an opioid overdose. On room air (FiO2 0.21, barometric pressure 760 mmHg, water vapour 47 mmHg, R =…
- Respiratory system: shunt and supplemental oxygen · ApplicationA neonate with cyanotic congenital heart disease and a right-to-left shunt stays cyanosed after breathing 100% oxygen for 10 minutes. What is the reason?
- Respiratory system: carbon monoxide poisoning · Multi-stepA 28-year-old man is found drowsy and confused beside a burning charcoal heater in a closed room in winter. Pulse oximetry reads 98% and arterial PaO2 is 95 mmHg. Which…
- Respiratory system: carbon dioxide transport · ApplicationIn systemic tissue capillaries, which event occurs inside the red cell as CO2 diffuses in from the tissues?
- Respiratory system: Haldane effect · ApplicationIn the pulmonary capillaries, oxygenation of haemoglobin promotes the release of CO2 from blood. Which explanation is correct?
- Respiratory system: vagal reflexes · ApplicationAfter bilateral cervical vagotomy in an experimental animal, breathing becomes slow and deep. Loss of which reflex best explains this change in breathing pattern?
- Respiratory system: peripheral chemoreceptors · Multi-stepA 35-year-old woman with severe iron deficiency has haemoglobin of 4 g/dL, so her arterial oxygen content is about one third of normal. At rest she is not hyperventilat…
- Respiratory system: closing capacity · ApplicationA 70-year-old man is anaesthetised and positioned supine. Which change contributes to his hypoxaemia?
- Respiratory system: hypoxic pulmonary vasoconstriction · ApplicationA man with chronic bronchitis has long-standing alveolar hypoxia and develops right-sided heart failure. Which mechanism links the two?
- Respiratory system: Bohr dead space · Multi-stepIn a resting adult, arterial PCO2 is 40 mmHg and mixed expired PCO2 is 28 mmHg. Tidal volume is 500 mL. Using the Bohr equation, what is the physiological dead space?
- Respiratory system: medullary rhythm generation · ApplicationA man given a large intravenous dose of morphine breathes slowly and then becomes apnoeic. Which site, rich in mu-opioid receptors, contains the neurons that generate t…
- Respiratory system: Cheyne-Stokes breathing · Multi-stepA 68-year-old man with severe left ventricular failure shows cycles of waxing and waning breathing separated by apnoeic periods. Which mechanism best explains this patt…
- Respiratory system: surface tension and lung recoil · Multi-stepAn excised lung is inflated and deflated first with air and then with saline. Compared with the air-filled lung, the saline-filled lung is much more compliant and shows…
- Respiratory system: diffusing capacity for carbon monoxide · Multi-stepA 32-year-old man with haemoptysis, haematuria and normal spirometry has a diffusing capacity for carbon monoxide (DLCO) above the predicted value. What explains the ra…
- Respiratory system: perfusion versus diffusion limitation · ApplicationAt rest, nitrous oxide equilibrates with capillary blood within the first part of its transit through the alveolar capillary, whereas carbon monoxide does not equilibra…
- Respiratory system: pulmonary vascular response to exercise · ApplicationDuring strenuous exercise cardiac output may rise three to four-fold, yet mean pulmonary arterial pressure increases only slightly. What is the main mechanism?
- Respiratory system: non-respiratory functions of the lung · ApplicationA 55-year-old hypertensive woman started on ramipril develops a persistent dry cough. Which non-respiratory pulmonary function explains this adverse effect?
- Respiratory system: diving and gas laws · ApplicationA diver breathes compressed air at 30 m depth (about 4 atmospheres absolute), then surfaces rapidly and develops joint pain and a rash. What is the mechanism?
- Respiratory system: acclimatisation to altitude · Multi-stepA trekker has spent a week at 4,000 metres. Compared with day one, her arterial blood gas shows a normal pH, a low PaCO2 and a low bicarbonate. Which process produced t…
- Respiratory system: emphysema mechanics · ApplicationA 62-year-old smoker has a barrel chest, prolonged expiration and a very low FEV1/FVC. Why do his small airways collapse during forced expiration?
- Respiratory system: shunt versus V/Q mismatch · Multi-stepA patient with lobar pneumonia has PaO2 of 55 mmHg on room air. After breathing 100 percent oxygen for 20 minutes, the PaO2 rises only to 70 mmHg. Which mechanism expla…
- Respiratory system: single-breath nitrogen test · ApplicationA subject takes one breath of 100 percent oxygen and then exhales slowly while nitrogen concentration is recorded. The volume exhaled before nitrogen reaches its alveol…
- Respiratory system: control of breathing · Multi-stepIn an animal experiment, the brainstem is cut at the mid-pontine level and both vagi are severed. The animal now takes prolonged inspiratory gasps with brief expiration…
- Respiratory system: diffusing capacity · Multi-stepA 45-year-old woman has exertional breathlessness. Spirometry and lung volumes are normal, but the diffusing capacity for carbon monoxide is markedly reduced. Which exp…
- Respiratory system: dynamic airway compression · Multi-stepIn a patient with emphysema, forced expiration causes airways to collapse early and expiratory flow reaches a plateau despite greater effort. What change explains the e…
- Respiratory system: work of breathing · Multi-stepPatients with pulmonary fibrosis breathe rapidly and shallowly. What is the physiological advantage of this pattern?
- Respiratory system: juxtacapillary receptors · ApplicationA patient with acute left heart failure feels short of breath with rapid shallow breathing. Which receptors, lying in the alveolar walls near the capillaries and stimul…
- Respiratory system: ventilatory response to metabolic acidosis · ApplicationA patient with severe diabetic ketoacidosis breathes deeply and rapidly with a PaCO2 of 20 mmHg. Which receptors provide the primary stimulus for this hyperventilation?
- Respiratory system: diffusion of carbon dioxide · ApplicationCarbon dioxide diffuses across the alveolar-capillary membrane about 20 times faster than oxygen, although its partial pressure gradient is much smaller. What is the ma…
- Respiratory system: West lung zones · ApplicationA ventilated patient with severe haemorrhage has a very low pulmonary arterial pressure, while positive pressure ventilation raises alveolar pressure. Which lung zone,…
- Respiratory system: types of hypoxia · Multi-stepAfter cyanide poisoning, a patient has severe tissue hypoxia but a normal PaO2, normal haemoglobin and unusually high mixed venous oxygen saturation. Which type of hypo…
- Respiratory system: cyanosis threshold · ApplicationA man with severe anaemia (haemoglobin 6 g/dL) has an arterial oxygen saturation of 60 percent but no cyanosis. What is the explanation?
- Respiratory system: effect of PEEP · ApplicationPositive end-expiratory pressure improves oxygenation in acute respiratory distress syndrome mainly by which mechanism?
- Respiratory system: oxygen therapy in chronic hypercapnia · Multi-stepA 66-year-old man with severe COPD and chronic CO2 retention is given high-flow oxygen and becomes drowsy; his PaCO2 rises from 60 to 85 mmHg. Besides a reduction in hy…
- Respiratory system: central hypoventilation and automatic breathing · ApplicationA 3-month-old infant breathes adequately when awake or stimulated, but during sleep the breathing becomes shallow or stops and the PaCO2 rises. Which description fits t…
- Respiratory system: phrenic nerve palsy · ApplicationA man develops breathlessness after cardiac surgery, and a chest radiograph shows an elevated left hemidiaphragm. On a sniff test under fluoroscopy, the left hemidiaphr…
- Respiratory system: closing volume and age · Multi-stepA 72-year-old woman is mildly hypoxaemic when lying supine under sedation, although her chest radiograph is clear. Which mechanism best explains this?
- Respiratory system: acetazolamide at altitude · ApplicationA trekker taking acetazolamide for prevention of acute mountain sickness ascends to 4000 m. How does the drug help acclimatisation?
- Respiratory system: absorption atelectasis · Multi-stepA post-operative patient is given 100 percent oxygen for many hours. A segmental bronchus is partly obstructed by secretions, and the lung volume of that segment gradua…
- Respiratory system: pneumothorax mechanics · ApplicationAfter a stab wound to the chest, a man has a collapsed right lung with the right chest wall sitting more expanded than the left. Which change explains these findings?
- Respiratory system: pulmonary vascular resistance and lung volume · Multi-stepA volunteer slowly inflates the lungs from functional residual capacity to total lung capacity. How does pulmonary vascular resistance change?
- Respiratory system: cough reflex · ApplicationA patient with an aspiration episode coughs forcefully. Which sequence describes the central part of the cough?
- Respiratory system: plethysmography versus helium dilution · Multi-stepIn a smoker with large emphysematous bullae, functional residual capacity measured by body plethysmography is much larger than that measured by helium dilution. What ex…
- Respiratory system: flow-volume loop in fixed upper airway obstruction · Multi-stepA woman with stridor after prolonged intubation has a flow-volume loop with a flat plateau of reduced peak flow on both the inspiratory and expiratory limbs. Which lesi…
- Respiratory system: inhaled nitric oxide in newborn pulmonary hypertension · Multi-stepA term newborn with persistent pulmonary hypertension is given inhaled nitric oxide, and pulmonary vascular resistance falls without a fall in systemic blood pressure.…
- Respiratory system: chronic mountain sickness · Multi-stepA 45-year-old man who has lived at 4,000 metres for 20 years has headache, cyanosis, a haematocrit of 72 percent and low arterial saturation. Which process explains the…
- Respiratory system: mechanism of high altitude pulmonary oedema · Multi-stepA fit climber ascends rapidly to 4,500 metres and develops breathlessness, cough with frothy sputum and a low saturation. The left atrial pressure is normal. Which mech…
- Respiratory system: physiological shunt in health · ApplicationIn a healthy person breathing air, arterial PO2 is a few mmHg lower than the calculated ideal alveolar PO2 even with well-matched ventilation and perfusion. What is the…
- Respiratory system: anaerobic threshold and ventilation · Multi-stepDuring an incremental treadmill test, minute ventilation starts rising out of proportion to oxygen uptake at a certain work rate. Which stimulus mainly accounts for thi…
- Respiratory system: apneusis after pontine section · Multi-stepIn an experimental animal, the brainstem is sectioned between the upper and middle pons and both vagi are cut. What breathing pattern results?
- Respiratory system: dead space after pulmonary embolism · ApplicationAfter a large pulmonary embolus, a ventilated patient has an end-tidal CO2 well below the arterial PCO2. Why?
- Respiratory system: ventilation in normal pregnancy · ApplicationA woman at 30 weeks of gestation is comfortable at rest. Arterial blood gas shows pH 7.44, PaCO2 30 mmHg and bicarbonate 20 mmol/L. How should this be interpreted?
- Respiratory system: lung volumes in obesity · ApplicationA 40-year-old man with a body mass index of 42 undergoes spirometry and lung volume measurement. Which pair of changes is typical?
- Respiratory system: ageing and elastic recoil · ApplicationA healthy non-smoker aged 78 has spirometry compared with that at age 25. Which pattern represents normal ageing?
- Respiratory system: central chemoreceptor adaptation in chronic hypercapnia · Multi-stepA man with long-standing severe chronic obstructive pulmonary disease retains CO2, but his ventilatory response to inhaled CO2 is blunted. Which adaptation contributes?
Blood and immunity58
- Blood and immunity: carbon monoxide poisoning · Multi-stepA family is brought in from a closed room with a coal stove, with headache and drowsiness. Pulse oximetry reads 98 percent but the patient is clearly unwell. Which stat…
- Blood and immunity: DIC versus TTP · Multi-stepA septic patient has oozing from venepuncture sites. Laboratory tests show prolonged PT and aPTT, low fibrinogen, raised D-dimer and thrombocytopenia. Which feature sep…
- Blood and immunity: Rh isoimmunisation · ApplicationAn Rh-negative primigravida delivers an Rh-positive baby. Why is anti-D immunoglobulin given to her within 72 hours?
- Blood and immunity: spleen function · ApplicationA 30-year-old man has his spleen removed after a road accident. Weeks later a blood smear shows small round dense basophilic inclusions in some red cells. What do these…
- Blood and immunity: platelet aggregation · Multi-stepA 6-year-old has had recurrent epistaxis and gum bleeding since infancy. Platelet count and morphology are normal and bleeding time is prolonged. Platelets fail to aggr…
- Blood and immunity: platelet adhesion · Multi-stepAn infant has thrombocytopenia with giant platelets and mucosal bleeding. Ristocetin does not agglutinate the platelets, and adding normal plasma does not correct this.…
- Blood and immunity: antigen presentation · ApplicationOn a lymph node section, a cell expresses MHC class II constitutively, takes up antigen in tissues, migrates to the node and is the most effective cell for priming naiv…
- Blood and immunity: neutrophil rolling · ApplicationIn acute bacterial infection, circulating neutrophils first roll slowly along the wall of the post-capillary venule before they stick firmly and cross it. Which molecul…
- Blood and immunity: erythrocyte sedimentation · ApplicationA patient with chronic inflammation has a markedly raised erythrocyte sedimentation rate. Which change in the blood chiefly accounts for this?
- Blood and immunity: thymic selection · Multi-stepDuring maturation in the thymus, a developing T cell whose receptor binds a self peptide-MHC complex with very high affinity is most likely to undergo which fate?
- Blood and immunity: initiation of coagulation · ApplicationAfter a vessel is cut, which event is the main trigger for coagulation in vivo?
- Blood and immunity: red cell oxidant defence · Multi-stepA 25-year-old man develops dark urine and jaundice two days after starting primaquine. His smear shows bite cells, and supravital staining shows blue-purple inclusions…
- Blood and immunity: fetal haemoglobin and sickling · ApplicationA child with sickle cell disease stays well during the first months of life and has the first painful crisis after about 6 months. Which feature of infant red cells exp…
- Blood and immunity: nuclear-cytoplasmic dissociation · ApplicationA marrow film shows large erythroid precursors with open, immature nuclear chromatin although the cytoplasm is well haemoglobinised. Which biochemical lesion explains t…
- Blood and immunity: haptoglobin in haemolysis · ApplicationA patient with a mechanical aortic valve has anaemia, a raised LDH and free haemoglobin in plasma. What is expected for serum haptoglobin, and why?
- Blood and immunity: platelet dense granules · Multi-stepA child with easy bruising and nosebleeds has a normal platelet count and a prolonged bleeding time. Aggregometry shows absent second-wave aggregation with epinephrine,…
- Blood and immunity: role of factor VIII · ApplicationA boy with recurrent haemarthroses has a prolonged aPTT with a normal PT and normal platelet count, and his factor VIII activity is under 1 percent. In the coagulation…
- Blood and immunity: heparin-induced thrombocytopenia · Multi-stepOn day 7 of unfractionated heparin after cardiac surgery, a man's platelet count falls from 250,000 to 80,000 per microlitre and he develops a new deep vein thrombosis.…
- Blood and immunity: activated protein C resistance · Multi-stepA 28-year-old woman has a deep vein thrombosis during pregnancy. PT and aPTT are normal, and protein C, protein S and antithrombin levels are normal, but the aPTT does…
- Blood and immunity: natural killer cell recognition · Multi-stepA virus-infected cell has down-regulated MHC class I to escape CD8 T cells. Which lymphocyte can still kill it, and why?
- Blood and immunity: type I hypersensitivity · ApplicationWithin minutes of a wasp sting, a man develops urticaria, wheeze and hypotension. Which immune mechanism accounts for these features?
- Blood and immunity: macrophage activation by interferon-gamma · ApplicationA boy has recurrent disseminated infection with weakly pathogenic mycobacteria. Genetic testing shows a defect in the receptor for the cytokine that Th1 cells use to ac…
- Blood and immunity: X-linked agammaglobulinaemia · Multi-stepA 9-month-old boy has recurrent otitis media and pneumonia from encapsulated bacteria after maternal IgG has waned. Flow cytometry shows almost no CD19-positive cells a…
- Blood and immunity: pharyngeal pouch development and immunity · ApplicationA newborn has tetany, a cardiac outflow tract defect and recurrent viral infections, and the chest radiograph shows no thymic shadow. Which developmental failure explai…
- Blood and immunity: lysosomal trafficking defect in phagocytes · Multi-stepA child with partial albinism and silvery hair has recurrent pyogenic infections, and blood films show giant cytoplasmic granules in neutrophils. Which defect underlies…
- Blood and immunity: hyperacute graft rejection · ApplicationWithin minutes of revascularisation, a transplanted kidney becomes mottled and cyanotic. Which mechanism is responsible?
- Blood and immunity: cross-matching · ApplicationA patient is to receive a red cell transfusion. In the major cross-match, which two components are mixed?
- Blood and immunity: affinity maturation · Multi-stepDuring a prolonged immune response, antibodies produced against the same antigen bind with progressively higher affinity. Which process in the germinal centre is respon…
- Blood and immunity: type I interferons · ApplicationA virus-infected cell releases a cytokine that makes neighbouring cells block viral protein synthesis and degrade viral RNA through protein kinase R and RNase L. Which…
- Blood and immunity: acute phase response · ApplicationIn a patient with sepsis, C-reactive protein and hepcidin rise sharply in the liver. Which cytokine is the main stimulus for this hepatic acute phase response?
- Blood and immunity: endothelial antithrombotic factors · ApplicationIntact vascular endothelium prevents platelet adhesion to the vessel wall. Which pair of endothelial products inhibits platelet activation?
- Blood and immunity: leukotrienes · ApplicationA man with asthma has bronchoconstriction that is not relieved by antihistamines but improves with montelukast. Which mediators are being blocked?
- Blood and immunity: lymphocyte homing · Multi-stepNaive lymphocytes continually leave the blood and enter lymph nodes. Through which structure and with which adhesion molecule do they cross?
- Blood and immunity: superantigens · Multi-stepA young woman using a tampon develops fever, a diffuse rash and hypotension. The responsible toxin binds MHC class II outside the peptide groove and the T-cell receptor…
- Blood and immunity: central tolerance and AIRE · Multi-stepA boy has chronic mucocutaneous candidiasis, hypoparathyroidism and autoimmune adrenal failure from a mutation in a transcription factor expressed in thymic medullary e…
- Blood and immunity: selective IgA deficiency · Multi-stepA woman with recurrent sinus infections and mild diarrhoea develops urticaria, wheeze and hypotension minutes into a blood transfusion. IgG and IgM are normal. Which fi…
- Blood and immunity: thrombomodulin · Multi-stepWhen thrombin binds thrombomodulin on intact endothelium, its action on the clotting system changes. What does the thrombin-thrombomodulin complex do?
- Blood and immunity: factor XIII · Multi-stepA newborn has prolonged bleeding from the umbilical stump and later a delayed haemorrhage after minor trauma. Platelet count, PT, aPTT and thrombin time are all normal.…
- Blood and immunity: lead and haem synthesis · ApplicationA 6-year-old living in an old house has abdominal colic, a pale appearance, basophilic stippling of red cells and a blue line on the gums. Which enzymes of haem synthes…
- Blood and immunity: osmotic fragility · ApplicationA 12-year-old has jaundice, splenomegaly and spherocytes on the smear, with a negative direct antiglobulin test. When his red cells are placed in graded hypotonic salin…
- Blood and immunity: paroxysmal nocturnal haemoglobinuria · Multi-stepA 30-year-old man has episodes of dark morning urine, unexplained abdominal vein thrombosis and a negative Coombs test. Which basic abnormality causes his red cells to…
- Blood and immunity: P2Y12 platelet receptor · ApplicationAfter coronary stenting, a patient is given aspirin together with a second antiplatelet drug that irreversibly blocks the receptor through which ADP from dense granules…
- Blood and immunity: Glanzmann thrombasthenia · Multi-stepA child has easy mucosal bleeding, a normal platelet count and a prolonged bleeding time. Platelets fail to aggregate with ADP, collagen and thrombin but agglutinate no…
- Blood and immunity: hereditary angioedema · Multi-stepA 22-year-old has recurrent non-itchy swelling of the face, bowel wall colic and laryngeal swelling after dental work. There is no urticaria, antihistamines and adrenal…
- Blood and immunity: adenosine deaminase deficiency · Multi-stepAn infant has persistent infections with almost no T or B lymphocytes. Lymphocytes accumulate deoxyadenosine triphosphate, which inhibits ribonucleotide reductase. Whic…
- Blood and immunity: serum sickness · ApplicationA man develops fever, an urticarial rash, joint pains and a fall in serum C3 eight days after receiving horse-derived antivenom. Which immune mechanism underlies his il…
- Blood and immunity: graft-versus-host disease · ApplicationTen days after allogeneic bone marrow transplantation, a patient develops a skin rash, jaundice and watery diarrhoea. Which cells in the graft mediate this complication?
- Blood and immunity: polycythaemia vera · Multi-stepA 58-year-old has facial plethora, itching after a hot bath, splenomegaly and a high haemoglobin. Which pattern of erythropoietin level and arterial oxygen saturation f…
- Blood and immunity: folate versus B12 deficiency · Multi-stepA chronic alcohol user has macrocytic anaemia with hypersegmented neutrophils but no neurological signs. Serum homocysteine is raised while methylmalonic acid is normal…
- Blood and immunity: chronic granulomatous disease · Multi-stepA boy has recurrent abscesses of the liver and lung caused by Staphylococcus aureus and Aspergillus. The nitroblue tetrazolium test fails to turn blue. Why are catalase…
- Blood and immunity: factor VII half-life · Multi-stepA patient is started on warfarin. Within 24 to 48 hours the prothrombin time lengthens, yet full antithrombotic protection is not yet present. Which clotting factor, wi…
- Blood and immunity: immune complex clearance · ApplicationA patient with systemic lupus erythematosus has low C3 and C4 with high anti-dsDNA titres, and immune complexes lodge in the glomeruli. Which immune mechanism produces…
- Blood and immunity: erythropoietin target cell · ApplicationIn a patient with chronic kidney disease, erythropoietin therapy raises the reticulocyte count. Which marrow cell type is the main target of erythropoietin?
- Blood and immunity: hydrops fetalis and haemoglobin Bart's · Multi-stepA fetus has hydrops, severe anaemia and a haemoglobin that is almost entirely made of four gamma chains. Which genetic defect underlies this?
- Blood and immunity: polysaccharide vaccine response · Multi-stepInfants respond poorly to a pure capsular polysaccharide vaccine but respond well when the same polysaccharide is chemically linked to a carrier protein. What is the ma…
- Blood and immunity: Wiskott-Aldrich syndrome · Multi-stepA 2-year-old boy has eczema, recurrent ear infections and bleeding with a low platelet count and unusually small platelets. A mutation in a protein regulating which cel…
- Blood and immunity: febrile transfusion reaction · ApplicationThirty minutes into a red cell transfusion, a patient develops chills and a 1.5 degree C rise in temperature, with no haemolysis, hypotension or urticaria. Which cause…
- Blood and immunity: marrow failure blood picture · ApplicationA patient has pancytopenia with a hypocellular, fat-replaced bone marrow and no abnormal cells. Which pair of findings is expected in the blood film and reticulocyte co…
Reproduction56
- Reproduction: 5-alpha reductase deficiency · Multi-stepA 46,XY child raised as a girl virilises at puberty, with a deeper voice, phallic growth and muscle development. Testes are present, serum testosterone is normal, dihyd…
- Reproduction: menopausal hormones · ApplicationA 52-year-old woman has not menstruated for 14 months and has hot flushes. Which hormone profile is expected?
- Reproduction: primary testicular failure · ApplicationA tall 24-year-old man with small firm testes, gynaecomastia and azoospermia has a 47,XXY karyotype and a low serum testosterone. Which hormonal pattern is expected?
- Reproduction: fertilisation · ApplicationWhich event follows the binding of a capacitated sperm to the zona pellucida of the oocyte?
- Reproduction: semen composition · Multi-stepA 29-year-old man with infertility has azoospermia, semen volume 0.8 mL, acidic pH and absent fructose. Testes are of normal size and FSH is normal. What is the most li…
- Reproduction: neural control of ejaculation · ApplicationAfter retroperitoneal lymph node dissection for a testicular tumour, a man has normal erections and orgasm but ejaculates no semen. Which pathway was most likely damaged?
- Reproduction: timing of ovulation · Multi-stepA woman has regular 35-day menstrual cycles. Assuming a normal luteal phase of 14 days, on which cycle day does ovulation most likely occur?
- Reproduction: onset of menstruation · ApplicationMenstruation begins at the end of a non-conception cycle because:
- Reproduction: two-cell theory of oestrogen synthesis · ApplicationIn the follicular phase, theca interna cells under LH stimulation make androstenedione. Where is it converted to oestradiol, and under which hormone?
- Reproduction: combined oral contraceptive · ApplicationA combined oral contraceptive pill prevents pregnancy chiefly by which mechanism?
- Reproduction: prolactin regulation · ApplicationA 26-year-old woman taking metoclopramide for nausea develops galactorrhoea and amenorrhoea. Serum prolactin is raised. Why?
- Reproduction: placental hormones and glucose · ApplicationA woman in the third trimester has a rising insulin requirement and develops gestational diabetes. Which placental hormone chiefly produces this insulin resistance?
- Reproduction: neonatal circulatory transition · ApplicationAfter a term baby's first breaths, the foramen ovale closes functionally. Which change is responsible?
- Reproduction: Kallmann syndrome · Multi-stepA 17-year-old boy has no pubertal development and cannot smell. Testosterone, LH and FSH are all low, other pituitary hormones are normal and pituitary MRI is normal. G…
- Reproduction: gonadal dysgenesis · ApplicationA 15-year-old girl has short stature, webbed neck, no breast development and primary amenorrhoea. FSH and LH are markedly high and oestradiol is low. Which mechanism ex…
- Reproduction: androgen insensitivity syndrome · Multi-stepAn 18-year-old with a female phenotype and well-developed breasts has scanty pubic hair, primary amenorrhoea, a blind vagina and no uterus. Karyotype is 46,XY, with hig…
- Reproduction: milk ejection reflex · ApplicationA breastfeeding mother is suddenly distressed by a loud argument. Her infant continues to suck, but milk flow stops although her milk production remains normal. What is…
- Reproduction: menstruation mechanism · ApplicationA woman with secondary amenorrhoea is given oral progestogen for 10 days. Bleeding occurs two days after stopping. What is the immediate mechanism?
- Reproduction: hCG and thyroid stimulation · Multi-stepA 26-year-old woman at 10 weeks of amenorrhoea has uterine size larger than dates, vaginal bleeding, a very high hCG, tremor, suppressed TSH and raised free T4. How doe…
- Reproduction: exogenous androgen effects · Multi-stepA 24-year-old bodybuilder using testosterone esters has small, soft testes, a very low sperm count, low LH and FSH, and breast tenderness. What best explains the infert…
- Reproduction: luteal-placental shift · ApplicationA woman at 6 weeks of pregnancy loses the pregnancy after removal of the corpus luteum, whereas the same procedure at 11 weeks does not end pregnancy. What explains the…
- Reproduction: lactational amenorrhoea · ApplicationA woman exclusively breastfeeding her 4-month-old infant remains amenorrhoeic and anovulatory. Which mechanism chiefly explains this lactational amenorrhoea?
- Reproduction: blood-testis barrier · ApplicationA 28-year-old man has severe oligospermia and high titres of antisperm antibodies after a crush injury to the testis. Which normal structure protects developing haploid…
- Reproduction: fetoplacental unit · ApplicationIn a pregnancy with fetal anencephaly, maternal urinary oestriol is very low although the placenta is otherwise normal. What is the most likely mechanism?
- Reproduction: pulsatile GnRH and puberty · ApplicationA 7-year-old girl with central precocious puberty is treated with a long-acting GnRH agonist, after which LH and FSH fall and breast development regresses. Why does a c…
- Reproduction: duration of spermatogenesis · ApplicationA 30-year-old man has a sperm count of 3 million/mL during sulfasalazine therapy, which is then stopped. About when should a repeat semen analysis be done to judge reco…
- Reproduction: ovulation trigger · ApplicationIn the late follicular phase, rising oestradiol above a sustained threshold produces a large pituitary release of LH. What is this type of control?
- Reproduction: androgen insensitivity · Multi-stepA phenotypically female 17-year-old has primary amenorrhoea, normal breast development, scanty pubic hair and a blind-ending vagina with no uterus. Karyotype is 46,XY.…
- Reproduction: fetoplacental unit · Multi-stepIn late pregnancy, a very low maternal oestriol level can suggest fetal compromise. Why does oestriol synthesis depend on both fetus and placenta?
- Reproduction: oogenesis · ApplicationAt the time of ovulation, at which stage of meiosis is the oocyte arrested?
- Reproduction: sexual differentiation · Multi-stepA 46,XY boy has normal testes and male external genitalia, and a uterus and fallopian tubes are found at hernia repair. Which hormone or receptor is defective?
- Reproduction: testicular endocrine function · Multi-stepA man has seminiferous tubule damage after mumps orchitis with intact Leydig cells. Which hormone profile is expected?
- Reproduction: temperature and spermatogenesis · ApplicationA man with untreated bilateral undescended testes has impaired spermatogenesis in adulthood. Which factor is chiefly responsible?
- Reproduction: cervical mucus at ovulation · ApplicationA woman notes clear, watery cervical mucus that stretches into a long thread (spinnbarkeit) and forms a fern pattern when dried on a slide. Which hormonal state does th…
- Reproduction: inhibin B feedback · ApplicationA 31-year-old infertile man has azoospermia and small testes. FSH is markedly raised while LH and testosterone are normal. Loss of which Sertoli cell product best expla…
- Reproduction: polycystic ovary syndrome · Multi-stepA 24-year-old obese woman has oligomenorrhoea, hirsutism and acanthosis nigricans. LH is raised relative to FSH and testosterone is raised. Which mechanism contributes…
- Reproduction: block to polyspermy · ApplicationAfter one sperm penetrates the oocyte, cortical granules release their contents into the perivitelline space. What is the functional result?
- Reproduction: effects of oestrogen loss · ApplicationA 55-year-old woman, five years after menopause, has osteopenia and a less favourable lipid profile. Which pair of oestrogen actions has been lost?
- Reproduction: onset of lactation · ApplicationProlactin is high through pregnancy, yet copious milk secretion begins only after delivery. What permits lactation to start?
- Reproduction: perimenopausal FSH rise · Multi-stepA 47-year-old woman has regular but shortening cycles. Her FSH is raised while LH and oestradiol are still normal. Which change is chiefly responsible for the early FSH…
- Reproduction: testis-determining gene · Multi-stepA 17-year-old with female external genitalia has primary amenorrhoea, no breast development, a uterus and tubes on ultrasound, streak gonads and a 46,XY karyotype. Whic…
- Reproduction: hyperprolactinaemic amenorrhoea · ApplicationA 28-year-old woman with a prolactinoma has amenorrhoea with low oestradiol and low LH and FSH. How does raised prolactin cause the amenorrhoea?
- Reproduction: onset of parturition · ApplicationNear term, the uterus becomes much more sensitive to oxytocin. Which change in the myometrium contributes?
- Reproduction: antenatal corticosteroids · ApplicationA woman at 30 weeks with threatened preterm labour is given betamethasone. Which fetal effect is intended?
- Reproduction: emergency contraception · ApplicationA woman takes levonorgestrel 1.5 mg within 24 hours of unprotected intercourse in mid-cycle. What is its main mechanism?
- Reproduction: oestrogen-androgen balance in men · Multi-stepA 55-year-old man with alcoholic cirrhosis develops gynaecomastia, testicular atrophy and loss of body hair. Which hormonal mechanism contributes?
- Reproduction: renal changes in pregnancy · Multi-stepA pregnant woman at 24 weeks has serum creatinine 0.5 mg/dL, lower than the usual adult range. Why?
- Reproduction: effect of the LH surge on the oocyte · ApplicationWhich event inside the primary oocyte is triggered by the preovulatory LH surge?
- Reproduction: suckling and prolactin · ApplicationHow does suckling cause a rapid rise in prolactin secretion?
- Reproduction: progesterone and smooth muscle · ApplicationA woman at 28 weeks has heartburn, constipation and mild ureteric dilatation on ultrasound. Which hormonal action contributes to these features?
- Reproduction: functional hypothalamic amenorrhoea · ApplicationA 21-year-old marathon runner with a BMI of 17 has stopped menstruating. Oestradiol, LH and FSH are low and prolactin is normal. What is the most likely mechanism?
- Reproduction: sperm capacitation · ApplicationEjaculated sperm cannot fertilise an oocyte until they have spent several hours in the female genital tract. What does this final maturation step involve?
- Reproduction: respiratory changes in pregnancy · Multi-stepA healthy woman at 30 weeks of gestation has arterial pH 7.44, PaCO2 30 mmHg and bicarbonate 20 mmol/L. Which hormone chiefly drives this normal change?
- Reproduction: oocyte arrest points · ApplicationA secondary oocyte is ovulated after the LH surge. At what stage is it arrested until fertilisation?
- Reproduction: effect of vasectomy on hormones · ApplicationA 35-year-old man has a vasectomy. Six months later, which finding is expected in his serum?
- Reproduction: testosterone synthesis in Leydig cells · Multi-stepIn a Leydig cell, LH binding raises cyclic AMP and promotes the first, rate-limiting step of steroid synthesis. What is that step?
General physiology46
- General physiology: Nernst potential · Multi-stepIn a mammalian neurone at 37 degrees C the intracellular K+ concentration is 150 mmol/L and the extracellular concentration is 5 mmol/L. Using the Nernst equation in th…
- General physiology: Na+-K+ ATPase and digoxin · ApplicationA 68-year-old man with chronic heart failure is started on digoxin. Which sequence best explains its positive inotropic effect on the myocardium?
- General physiology: secondary active transport · ApplicationA 5-year-old child with cholera has profuse watery diarrhoea. Oral rehydration solution is effective even though the toxin drives secretion, mainly because:
- General physiology: osmolarity calculation · Multi-stepA 55-year-old man has serum sodium 140 mmol/L, glucose 180 mg/dL and blood urea nitrogen 28 mg/dL. Using osmolarity = 2 x Na + glucose/18 + BUN/2.8, what is his calcula…
- General physiology: indicator dilution · Multi-stepTo measure plasma volume, 15 mg of Evans blue dye is injected intravenously. After complete mixing the plasma concentration is 0.5 mg/dL. Ignoring any loss of dye from…
- General physiology: fluid compartment shifts · ApplicationA healthy adult is given 1 litre of 0.9% saline intravenously and allowed to equilibrate. Which change is expected?
- General physiology: excitability and potassium · ApplicationA 60-year-old man with renal failure has serum potassium of 7.2 mmol/L and generalised muscle weakness. Which mechanism explains the weakness?
- General physiology: calcium and nerve excitability · ApplicationA 30-year-old woman develops perioral tingling and carpopedal spasm after total thyroidectomy. Serum calcium is 1.7 mmol/L. How does low extracellular calcium cause tet…
- General physiology: neuromuscular transmission defect · Multi-stepA 62-year-old smoker has proximal leg weakness, dry mouth and absent tendon reflexes. Strength improves briefly after sustained effort, and high-frequency repetitive ne…
- General physiology: inhibitory synapse · ApplicationA patient in status epilepticus is given intravenous lorazepam. Which postsynaptic event mediates its inhibitory effect?
- General physiology: heat loss · ApplicationA labourer works in a furnace room where the air temperature is 40 degrees C, above his skin temperature of about 33 degrees C. Which mechanism remains the main route o…
- General physiology: Gibbs-Donnan effect · ApplicationAnimal cells contain large, negatively charged proteins that cannot cross the plasma membrane. If the Na+-K+ ATPase of a cell were completely blocked for several hours,…
- General physiology: effective osmoles and tonicity · ApplicationA 62-year-old man with advanced chronic kidney disease has blood urea 280 mg/dL and a measured plasma osmolality of 330 mOsm/kg, with a normal serum sodium. Which state…
- General physiology: gain of a feedback system · Multi-stepIn an experiment a disturbance would raise mean arterial pressure by 75 mmHg if the baroreceptor reflex were disabled. With the reflex intact, the pressure rises by onl…
- General physiology: Fick's law of diffusion · ApplicationIn a patient with advanced pulmonary fibrosis and emphysematous change, the blood-gas barrier is twice as thick and the effective surface area is half of normal. Other…
- General physiology: body fluid compartment volumes · Multi-stepIn a healthy 70 kg man, total body water measured by deuterium oxide is 42 L, extracellular fluid space by inulin is 14 L, and plasma volume by Evans blue is 3 L. His h…
- General physiology: osmoreceptors and the lamina terminalis · ApplicationNeurons of the organum vasculosum of the lamina terminalis respond to changes in plasma osmolality of only 1 to 2 percent and drive thirst and ADH release. What allows…
- General physiology: lymphatic obstruction and oedema · Multi-stepA 40-year-old man from a filariasis-endemic area has gross swelling of the left leg. Aspirated interstitial fluid has a high protein concentration. Which mechanism best…
- General physiology: cell cycle · ApplicationA woman with breast cancer is given a CDK4/6 inhibitor. At which point of the cell cycle does the drug arrest cells?
- General physiology: positive feedback in labour · ApplicationDuring labour the fetal head stretches the cervix, which increases oxytocin release, which strengthens uterine contractions and pushes the head harder against the cervi…
- General physiology: diffusion across membranes · ApplicationTwo uncharged drugs of similar molecular size are given at the same plasma concentration, and both cross the cell membrane only by simple diffusion. Drug A has an oil-w…
- General physiology: insulin receptor signalling · ApplicationIn a skeletal muscle cell, insulin increases glucose uptake by promoting GLUT4 insertion into the plasma membrane. Which initial signalling step follows insulin binding…
- General physiology: receptor-mediated endocytosis · ApplicationA 10-year-old boy has tendon xanthomas and a plasma LDL cholesterol of 600 mg/dL. His LDL receptors reach the cell surface and bind LDL normally, but fail to cluster in…
- General physiology: cyclic GMP signalling · ApplicationA patient with angina places a nitroglycerin tablet under the tongue and the chest pain eases as veins dilate. The released nitric oxide relaxes smooth muscle mainly by…
- General physiology: pure water excess · Multi-stepAfter a marathon, a runner drinks several litres of plain water. His plasma sodium falls to 125 mmol/L. By what pattern of fluid shift does the added water distribute?
- General physiology: steroid hormone receptors · ApplicationA patient started on oral prednisolone notices that the anti-inflammatory benefit appears over hours to days rather than within seconds. What does this delay reflect?
- General physiology: Goldman-Hodgkin-Katz equation · ApplicationDuring the upstroke of a nerve action potential, sodium permeability rises sharply while potassium permeability is unchanged. A student wants one equation that predicts…
- General physiology: non-shivering thermogenesis · ApplicationA healthy full-term newborn kept in a cool room maintains core temperature without shivering. Which process in brown adipose tissue accounts for the heat produced?
- General physiology: heat acclimatisation · ApplicationAfter two weeks of working in a hot, humid factory, a worker begins sweating earlier and more profusely, but his sweat is much more dilute in sodium. Which hormone medi…
- General physiology: pertussis toxin and Gi · ApplicationA 4-month-old unvaccinated infant has paroxysmal coughing ending in an inspiratory whoop. The toxin of the causative organism ADP-ribosylates the alpha subunit of a G p…
- General physiology: heat stroke versus fever · Multi-stepA 72-year-old man living alone is found confused during a heat wave. His core temperature is 41.2 degrees C, his skin is hot and dry, and antipyretics do not lower the…
- General physiology: peroxisomal function · ApplicationA hypotonic neonate has a high forehead, hepatomegaly and seizures. Plasma shows accumulation of unusual long fatty acids, and liver electron microscopy shows absence o…
- General physiology: intrinsic pathway of apoptosis · ApplicationAfter severe DNA damage, a cell's mitochondria release a protein into the cytosol that binds Apaf-1 and activates caspase-9, committing the cell to apoptosis. Which pro…
- General physiology: chloride gradient in immature neurones · Multi-stepIn immature cortical neurones, high NKCC1 activity keeps intracellular chloride above its equilibrium level. What happens when GABA-A receptors open in these cells?
- General physiology: feedforward control · ApplicationA sprinter's heart rate and ventilation rise at the starting blocks, before muscle activity has altered blood gases or pressure. Which control principle explains this e…
- General physiology: receptor desensitisation · ApplicationA patient with asthma on regular high-dose salbutamol finds the bronchodilator response gradually weakening although the dose is unchanged. Which cellular mechanism bes…
- General physiology: JAK-STAT signalling · ApplicationGrowth hormone receptors have no intrinsic enzyme activity. After the hormone binds, which mechanism transmits the signal into the cell?
- General physiology: mechanism of antipyretic action · ApplicationA febrile child's temperature falls after a dose of paracetamol. Which action best explains this?
- General physiology: brain adaptation to chronic hyponatraemia · Multi-stepA 45-year-old man with chronic alcohol use and serum sodium of 108 mmol/L for several days has it corrected to 125 mmol/L within 12 hours. Two days later he develops dy…
- General physiology: body water in obesity · ApplicationTwo men weigh the same, but one is lean and the other markedly obese. Compared with the lean man, the obese man will have which finding on total body water measurement?
- General physiology: heat loss in water · ApplicationA man falls into a lake at 20 degrees C and becomes hypothermic far sooner than he would have standing in still air at the same temperature. Which property of the mediu…
- General physiology: dextrose infusion distribution · Multi-stepA patient is given 1 litre of 5% dextrose in water over a few hours. After the glucose is metabolised, roughly how is the remaining free water distributed between body…
- General physiology: mitochondrial inheritance · ApplicationA mother with lactic acidosis, stroke-like episodes and myopathy passes the disease to all her children, whereas an affected father in another family passes it to none.…
- General physiology: sweat gland ion handling · ApplicationA 3-year-old with recurrent chest infections and greasy stools has very salty-tasting sweat. Which defect in the sweat gland explains the high sweat chloride?
- General physiology: calcium extrusion from myocytes · ApplicationIn a cardiac myocyte, most of the calcium that entered the cytosol during systole is removed across the sarcolemma by a transporter that uses the inward sodium gradient…
- General physiology: extrinsic apoptosis · Multi-stepA cytotoxic T cell binds Fas ligand on its surface to Fas on a virus-infected cell, and the target dies by apoptosis without mitochondrial involvement as the first step…
Nerve and muscle45
- Nerve and muscle: synaptic integration · Multi-stepA motor neuron at -70 mV has a threshold of -55 mV. Four excitatory synapses fire together, each producing a 5 mV EPSP, while one inhibitory synapse fires and produces…
- Nerve and muscle: use-dependent sodium channel block · ApplicationLidocaine given intravenously suppresses ventricular tachycardia in ischaemic myocardium, but has little effect on the normal atrial rhythm at a rate of 70 per minute.…
- Nerve and muscle: differential nerve block · ApplicationDuring the onset of a spinal anaesthetic with bupivacaine, a patient first feels warmth in the legs and can no longer feel a pinprick, yet can still move the toes. What…
- Nerve and muscle: local anaesthetic and tissue pH · ApplicationA surgeon infiltrates lidocaine (pKa 7.9) into an acutely infected, acidic abscess and the block is poor. Which mechanism best explains this?
- Nerve and muscle: extrajunctional receptors · Multi-stepA burns victim is paralysed with succinylcholine for surgery three weeks after injury. Within minutes serum potassium rises sharply and arrhythmia follows. Which change…
- Nerve and muscle: compound action potential · ApplicationDuring a nerve conduction study of the median nerve, the recorded compound action potential grows larger as stimulus intensity is increased and then stops growing. What…
- Nerve and muscle: organophosphate poisoning · Multi-stepA farmer sprays a pesticide without protection and arrives with sweating, miosis and fasciculations, followed by flaccid weakness of the respiratory muscles. What expla…
- Nerve and muscle: multi-unit smooth muscle · ApplicationA smooth muscle preparation has fibres that each receive their own nerve ending, few gap junctions, and graded contraction depending on how many fibres are stimulated.…
- Nerve and muscle: myelination in CNS and PNS · ApplicationIn a patient with a demyelinating disease of the optic nerve, loss of which cell's processes explains the conduction defect, given that one such cell can myelinate segm…
- Nerve and muscle: degrees of nerve injury · Multi-stepAfter a crush injury to the radial nerve, a man has wrist drop. The axons are interrupted but the endoneurial tubes and connective tissue sheaths remain intact. Which o…
- Nerve and muscle: edrophonium test · Multi-stepA 30-year-old woman with fatigable ptosis has her eyelid droop reverse for a few minutes after an intravenous dose of edrophonium. How does the drug produce this improv…
- Nerve and muscle: organophosphate poisoning · ApplicationA farmer who sprayed pesticide has salivation, lacrimation, small pupils, bradycardia and muscle fasciculations followed by weakness. Which enzyme is inhibited, and why…
- Nerve and muscle: dystrophin · ApplicationA 5-year-old boy has difficulty rising from the floor, calf enlargement and a creatine kinase about twenty times normal. Which protein function is lost?
- Nerve and muscle: myotonia congenita · Multi-stepA 15-year-old has difficulty releasing his grip after a handshake, which improves with repeated movement. EMG shows repetitive discharges that wax and wane. Which chann…
- Nerve and muscle: strychnine · ApplicationA man develops violent generalised convulsions with preserved consciousness after ingesting a rodenticide. The poison acts at which site?
- Nerve and muscle: presynaptic inhibition · Multi-stepIn the dorsal horn, an axo-axonal GABAergic synapse onto a primary afferent terminal reduces transmitter release without changing the postsynaptic membrane potential. H…
- Nerve and muscle: temperature and nerve conduction · ApplicationA technician warms a cold limb before nerve conduction studies. Why does cooling falsely suggest a neuropathy?
- Nerve and muscle: potassium channels in demyelinated axons · Multi-stepIn multiple sclerosis, fampridine (4-aminopyridine) can improve walking speed. Which action explains the benefit?
- Nerve and muscle: depolarising versus non-depolarising block · Multi-stepDuring neuromuscular monitoring after a drug, train-of-four stimulation shows each twitch smaller than the last, and the response improves after a tetanic burst. Which…
- Nerve and muscle: miniature end-plate potentials · ApplicationAt a resting neuromuscular junction, a microelectrode records small spontaneous depolarisations of about 0.4 mV, each of similar size. What do these represent?
- Nerve and muscle: safety factor at the end plate · ApplicationWhy does every motor nerve action potential normally produce a muscle action potential at the neuromuscular junction?
- Nerve and muscle: end-plate reversal potential · Multi-stepThe acetylcholine-gated channel at the motor end plate is about equally permeable to sodium and potassium. Towards what membrane potential does the end plate move durin…
- Nerve and muscle: recurrent inhibition by Renshaw cells · ApplicationCollaterals of alpha motor neurone axons excite spinal interneurones that release glycine onto the same motor neurone and its neighbours. Which cells are these?
- Nerve and muscle: occlusion in neuronal pools · Multi-stepStimulating afferent A alone discharges 6 neurones in a pool, and afferent B alone discharges 6 neurones, some of them the same ones. Stimulating A and B together disch…
- Nerve and muscle: retrograde neurotrophin signalling · ApplicationSympathetic and small sensory neurones survive only if their targets supply a growth factor that is taken up at the axon terminal. How does the survival signal reach th…
- Nerve and muscle: hypokalaemic weakness · ApplicationA patient on a potent diuretic has serum potassium of 2.4 mmol/L and generalised muscle weakness. Why does a low extracellular potassium cause weakness?
- Nerve and muscle: magnesium and neuromuscular transmission · ApplicationA woman with pre-eclampsia receiving intravenous magnesium sulphate loses her knee-jerk reflexes. How does high extracellular magnesium reduce neuromuscular transmission?
- Nerve and muscle: carnitine shuttle in muscle · Multi-stepA 22-year-old has muscle pain and dark urine after prolonged exercise during a fast. Venous lactate rises normally during ischaemic forearm exercise, and glycogen store…
- Nerve and muscle: SNARE proteins and calcium sensing · ApplicationAt the motor nerve terminal, which protein acts as the calcium sensor that triggers fusion of synaptic vesicles with the plasma membrane?
- Nerve and muscle: smooth muscle stress relaxation · ApplicationWhen the bladder is slowly filled, its wall tension rises initially and then falls back over the next minute although volume stays constant. What property of visceral s…
- Nerve and muscle: chromatolysis · ApplicationTwo weeks after crush injury to the sciatic nerve, a biopsy of the corresponding spinal motor neurone cell bodies shows swelling, an eccentric nucleus and dispersed Nis…
- Nerve and muscle: hypercalcaemia and excitability · Multi-stepA patient with a calcium of 3.4 mmol/L from hyperparathyroidism is lethargic with hypotonia and depressed tendon reflexes. How does high extracellular calcium reduce ne…
- Nerve and muscle: acetylcholine synthesis · ApplicationA drug blocks the rate-limiting step in acetylcholine production at the motor nerve terminal, so stores run down during repeated firing. Which step is blocked?
- Nerve and muscle: fast glycolytic fibre profile · ApplicationA biopsy from an elite sprinter's lateral thigh muscle is examined. Which combination of features would be expected in the predominant fibre type?
- Nerve and muscle: nerve conduction studies · Multi-stepA nerve conduction study in a patient with progressive limb weakness shows markedly reduced compound muscle action potential amplitude with only slightly reduced conduc…
- Nerve and muscle: hyperkalaemia and excitability · Multi-stepA patient with a serum potassium of 7.5 mmol/L has generalised muscle weakness. Why does persistently raised extracellular potassium reduce the excitability of skeletal…
- Nerve and muscle: smooth muscle latch state · ApplicationA blood vessel wall can maintain tone for long periods using very little ATP and low calcium. Which feature of smooth muscle is responsible?
- Nerve and muscle: neural adaptation to training · ApplicationA previously untrained man starts resistance training and his lifting strength rises considerably within the first 3 weeks, although his muscle bulk is unchanged. What…
- Nerve and muscle: Guillain-Barre conduction · Multi-stepA patient with ascending weakness after a diarrhoeal illness has absent reflexes and slowed conduction velocities with conduction block on nerve testing. Why does segme…
- Nerve and muscle: Schwann cell role in regeneration · ApplicationAfter a clean transection of a peripheral nerve is surgically repaired, axons can regrow along the distal stump. Which cells chiefly provide the guiding channels (bands…
- Nerve and muscle: succinylcholine versus rocuronium · Multi-stepTwo patients undergo surgery. One receives rocuronium and the other succinylcholine. On a train-of-four test, which finding distinguishes the early block produced by su…
- Nerve and muscle: skeletal muscle hypertrophy mechanism · ApplicationWhy does a muscle subjected to chronic resistance exercise enlarge in adults?
- Nerve and muscle: nerve injury grading · Multi-stepAfter a severe traction injury, a nerve shows complete loss of axons and its connective tissue sheaths are intact. Which outcome is most likely if the cause is removed?
- Nerve and muscle: electrical synapse · ApplicationReflex escape circuits in some animals use synapses in which impulses pass between neurones with almost no delay and in both directions. Which structure forms these syn…
- Nerve and muscle: after-hyperpolarisation · ApplicationIn a neurone, the membrane potential briefly falls below the resting level after repolarisation. What mainly causes this undershoot?
Endocrinology44
- Endocrinology: thyroid hormone actions · ApplicationA woman with thyrotoxicosis has resting tachycardia, heat intolerance and raised oxygen consumption although plasma catecholamines are normal. Which actions of thyroid…
- Endocrinology: cortisol rhythm · ApplicationA 35-year-old woman with weight gain and striae is being screened for Cushing syndrome. Which test best uses the normal physiology of cortisol secretion?
- Endocrinology: somatostatin · ApplicationA man with acromegaly treated with octreotide develops steatorrhoea and gallstones. Which physiological action of somatostatin analogues explains this?
- Endocrinology: growth hormone · Multi-stepA 9-year-old boy with short stature has an undetectable random serum growth hormone. Why is serum IGF-1 preferred as the first screening test for deficiency?
- Endocrinology: adrenal medulla · Multi-stepWhy does the adrenal medulla secrete mainly adrenaline (about 80 percent) rather than noradrenaline?
- Endocrinology: factitious thyrotoxicosis · Multi-stepA 35-year-old nurse has palpitations, weight loss and tremor. TSH is suppressed and free T4 raised. The thyroid is not palpable, radioiodine uptake is very low and seru…
- Endocrinology: congenital hypothyroidism · ApplicationA 3-week-old baby has prolonged jaundice, a large tongue, constipation and a hoarse cry. Why is early detection by newborn screening important?
- Endocrinology: HbA1c limitations · Multi-stepA diabetic patient with a recent haemolytic episode has a very low HbA1c, which does not match his high home glucose readings. What explains the mismatch?
- Endocrinology: hyperosmolar hyperglycaemic state · Multi-stepA 70-year-old with type 2 diabetes has glucose 900 mg/dL, osmolality 340 mOsm/kg and marked dehydration, but no ketones and a normal pH. Why is ketoacidosis absent?
- Endocrinology: hypocalcaemic tetany · ApplicationAfter total thyroidectomy a woman develops perioral tingling. Inflating a blood pressure cuff on her arm above systolic pressure for three minutes produces carpal spasm…
- Endocrinology: neonate of a diabetic mother · ApplicationA macrosomic infant of a mother with poorly controlled diabetes becomes jittery with a blood glucose of 20 mg/dL at 2 hours of life. Why?
- Endocrinology: thyroid hormone metabolism · ApplicationMost circulating triiodothyronine, the active thyroid hormone, arises from which process?
- Endocrinology: amylin · ApplicationA peptide co-secreted with insulin from pancreatic beta cells slows gastric emptying and suppresses post-meal glucagon release, and a synthetic analogue is used as an a…
- Endocrinology: counter-regulation of hypoglycaemia · ApplicationIn a healthy person with falling blood glucose after an insulin injection, which hormone is released first and most rapidly to raise glucose?
- Endocrinology: biphasic insulin secretion · ApplicationAfter an intravenous glucose load in a healthy person, insulin secretion shows a sharp peak within 5 to 10 minutes followed by a slower, sustained rise. What does the f…
- Endocrinology: FGF23 · Multi-stepWhich osteocyte-derived hormone lowers plasma phosphate by reducing phosphate reabsorption in the proximal tubule while also suppressing renal 1-alpha-hydroxylase?
- Endocrinology: oestrogen and epiphyseal closure · ApplicationIn both boys and girls, the pubertal growth spurt ends when the epiphyses fuse. Which hormone is chiefly responsible for epiphyseal closure?
- Endocrinology: non-thyroidal illness · Multi-stepA 62-year-old man in intensive care with severe sepsis has a normal TSH, low total and free T3, low-normal T4 and a raised reverse T3. He has no thyroid disease. Which…
- Endocrinology: adrenal medulla and catecholamine excess · Multi-stepA 40-year-old woman with episodic headache, sweating and palpitations has paroxysmal hypertension, raised urinary metanephrines and an adrenal mass. A beta-blocker give…
- Endocrinology: apparent mineralocorticoid excess · Multi-stepA 45-year-old man who eats large amounts of liquorice sweets has hypertension, hypokalaemia and metabolic alkalosis, with low plasma renin and low aldosterone. Which me…
- Endocrinology: humoral hypercalcaemia of malignancy · Multi-stepA 60-year-old smoker with squamous cell carcinoma of the lung has serum calcium 13.5 mg/dL, low serum phosphate and a suppressed PTH. Which tumour product most likely c…
- Endocrinology: PTH resistance · Multi-stepA 12-year-old with short stature, a round face and short fourth metacarpals has low serum calcium, high phosphate and a high PTH. Infused PTH causes no rise in urinary…
- Endocrinology: pituitary vulnerability in pregnancy · ApplicationAfter massive postpartum haemorrhage with shock, a woman cannot breastfeed and her periods never resume. Which feature of the pregnant pituitary makes it especially vul…
- Endocrinology: pineal and melatonin · ApplicationMelatonin secretion rises sharply at night and is suppressed by bright light. Which pathway drives the nocturnal rise?
- Endocrinology: adrenal steroidogenesis · Multi-stepA 46,XY infant has female-appearing genitalia and salt wasting. Cortisol, aldosterone and sex steroids are all low, ACTH and renin are high, and imaging shows enlarged…
- Endocrinology: congenital adrenal enzyme defects · Multi-stepA 16-year-old 46,XX girl has hypertension, hypokalaemia, absent breast development and primary amenorrhoea. Cortisol and sex steroids are low, ACTH is high, deoxycortic…
- Endocrinology: pancreatic hormone response to protein · ApplicationA healthy adult eats a meal of pure protein. Insulin secretion rises, yet plasma glucose does not fall. Which response prevents hypoglycaemia?
- Endocrinology: exercise and glucose uptake · Multi-stepDuring prolonged moderate exercise, glucose uptake by working skeletal muscle rises even though plasma insulin falls. What explains the increased uptake?
- Endocrinology: glucocorticoid effects on blood · ApplicationA patient on high-dose prednisolone for two weeks has a total leukocyte count of 14,000 per microlitre. Which differential pattern is most likely due to the glucocortic…
- Endocrinology: HPA axis suppression · Multi-stepA 50-year-old man who has taken prednisolone daily for eight months stops it abruptly and develops hypotension, vomiting and hypoglycaemia. Which change in the axis exp…
- Endocrinology: thyroid hormone and lipids · ApplicationA 45-year-old woman with fatigue and cold intolerance has a raised TSH and low free T4. Her LDL cholesterol is also raised. Why?
- Endocrinology: growth hormone and glucose · ApplicationA 30-year-old man with acromegaly has a raised fasting glucose. Which action of growth hormone contributes to this?
- Endocrinology: secondary hyperaldosteronism · Multi-stepA patient with decompensated cirrhosis and ascites has hypokalaemia, high aldosterone and high plasma renin activity. Why does this differ from primary aldosteronism, i…
- Endocrinology: insulin and lipolysis · ApplicationA patient with untreated type 1 diabetes has high circulating free fatty acids. Which change in adipose tissue explains the excessive lipolysis?
- Endocrinology: beta cell glucose sensing · ApplicationPancreatic beta cells release insulin in proportion to blood glucose. Which feature allows them to act as glucose sensors?
- Endocrinology: autoimmune thyroiditis · ApplicationA 38-year-old woman has a firm, painless, diffusely enlarged thyroid, a raised TSH and a low free T4. Biopsy shows dense lymphocytic infiltration with germinal centres…
- Endocrinology: loss of cortisol feedback after adrenalectomy · ApplicationA woman who underwent bilateral adrenalectomy for pituitary-dependent Cushing disease later develops darkening of the skin and an enlarging sellar mass with a very high…
- Endocrinology: dawn phenomenon · Multi-stepA man with type 1 diabetes on basal insulin has a fasting glucose of 190 mg/dL, but a 3 a.m. glucose of 105 mg/dL, with a steady rise after about 4 a.m. Which physiolog…
- Endocrinology: cortisol-binding globulin · ApplicationA woman taking oral oestrogen has a high total serum cortisol, but normal 24-hour urinary free cortisol, normal late-night salivary cortisol and no Cushingoid features.…
- Endocrinology: delayed counter-regulation of hypoglycaemia · ApplicationAfter glucagon and adrenaline have acted in the first minutes of insulin-induced hypoglycaemia, which pair of hormones sustains glucose recovery over the next few hours…
- Endocrinology: resistance to thyroid hormone · Multi-stepA 9-year-old has a small goitre, tachycardia and hyperactivity. Free T4 and free T3 are raised, but TSH is within the normal range, and pituitary MRI is normal. His fat…
- Endocrinology: TSH as a screening test · ApplicationIn suspected primary hypothyroidism, a serum TSH is preferred to a free T4 as the first screening test. Which relationship supports this?
- Endocrinology: secondary adrenal insufficiency · Multi-stepA woman 6 months after pituitary surgery has fatigue, hypotension and a low morning cortisol with low ACTH. Her serum potassium is normal. Why is potassium handling pre…
- Endocrinology: subacute thyroiditis · Multi-stepA woman has fever, a tender thyroid and palpitations two weeks after a viral illness. Free T4 is raised, TSH is suppressed and the ESR is high, but thyroid radioiodine…
Neurophysiology36
- Neurophysiology: cerebellum · ApplicationA patient has a tremor that appears only on reaching for an object and worsens as the finger approaches the target, with past-pointing and dysdiadochokinesia on the rig…
- Neurophysiology: basal ganglia · Multi-stepLoss of dopaminergic neurons of the substantia nigra pars compacta causes bradykinesia. Which change in the basal ganglia circuit explains this?
- Neurophysiology: spinal cord hemisection · ApplicationA man has a stab injury causing right-sided hemisection of the spinal cord at T10. Which finding is expected?
- Neurophysiology: syringomyelia · ApplicationA 28-year-old has painless burns on both hands and bilateral loss of pain and temperature over the shoulders and arms, but retains light touch and vibration. What expla…
- Neurophysiology: inhibitory synapse · ApplicationA patient with an acute seizure receives intravenous lorazepam. How does the drug enhance inhibitory synaptic transmission?
- Neurophysiology: hypothalamus · ApplicationAn 8-year-old develops ravenous appetite and rapid weight gain after resection of a craniopharyngioma that has damaged the medial hypothalamus. Which nucleus is most li…
- Neurophysiology: thalamic relay · ApplicationA lacunar infarct causes loss of all sensory modalities over the left side of the trunk and limbs, but the left face is spared. Which structure is affected?
- Neurophysiology: memory · ApplicationAfter bilateral medial temporal lobe resection for epilepsy, a man cannot form new long-term declarative memories but recalls his childhood and can learn new motor skil…
- Neurophysiology: language areas · ApplicationAfter a stroke in the inferior division of the middle cerebral artery, a woman speaks fluently with paraphasic errors and cannot understand commands. Which area is dama…
- Neurophysiology: dorsal column loss · ApplicationA 55-year-old man with tabes dorsalis stands steadily with eyes open but sways and falls when he closes them. Which mechanism explains this Romberg sign?
- Neurophysiology: decerebrate rigidity · ApplicationA patient has a brainstem lesion below the red nucleus, with extension of all four limbs and the neck arched back. Which motor outflow is acting unopposed?
- Neurophysiology: aphasia · Multi-stepAfter a left parietal stroke, a man speaks fluently with occasional wrong-word errors and understands commands, but cannot repeat the phrase 'no ifs, ands or buts'. Whi…
- Neurophysiology: memory and long-term potentiation · ApplicationA patient with bilateral hippocampal damage after herpes encephalitis cannot form new declarative memories. Which cellular event underlies hippocampal long-term potenti…
- Neurophysiology: referred pain · ApplicationA 58-year-old man has retrosternal pain during exertion that radiates to the inner side of the left arm. Which mechanism best explains the radiation?
- Neurophysiology: lower motor neurone lesion · ApplicationA 3-year-old unvaccinated child has fever followed by sudden asymmetrical weakness of the right leg. On examination there is reduced tone, absent knee and ankle jerks a…
- Neurophysiology: reticular activating system · ApplicationA 55-year-old hypertensive man collapses and is deeply unresponsive. MRI shows a small haemorrhage in the dorsal upper pons and midbrain, with both cerebral hemispheres…
- Neurophysiology: tonic and phasic receptors · ApplicationA blind person reads Braille using the fingertip, feeling edges and points of raised dots with sustained pressure. Which receptors mainly signal this?
- Neurophysiology: clonus · ApplicationA patient after a stroke has rhythmic, repeated contractions of the calf when the foot is briskly dorsiflexed and held. Which mechanism underlies this sign?
- Neurophysiology: frontal lobe lesion · ApplicationAfter a bilateral injury to the prefrontal cortex, a previously reserved man becomes socially disinhibited, makes poor decisions and shows little concern for consequenc…
- Neurophysiology: glutamate excitotoxicity · ApplicationIn the penumbra around a cerebral infarct, extracellular glutamate remains high and neurones die despite partial blood flow. Which sequence explains the neuronal death?
- Neurophysiology: Monro-Kellie doctrine · ApplicationA slowly enlarging intracranial mass causes no rise in pressure at first. Which mechanism buffers the early rise in volume?
- Neurophysiology: cerebellar climbing fibres · Multi-stepIn the cerebellum, a single Purkinje cell receives input from one climbing fibre and thousands of parallel fibres. From which structure do climbing fibres arise, and wh…
- Neurophysiology: cerebrospinal fluid composition · ApplicationCompared with plasma, normal cerebrospinal fluid has which composition?
- Neurophysiology · ApplicationWhat ion influx produces the rapid depolarization of a typical neuron?
- Neurophysiology · ApplicationWhat neurotransmitter is released at the skeletal neuromuscular junction?
- Neurophysiology · ApplicationWhat ion efflux primarily repolarizes a typical neuronal action potential?
- Neurophysiology · ApplicationWhat is the main function of myelin around many axons?
- Neurophysiology · ApplicationWhat happens at a chemical synapse when calcium enters the presynaptic terminal?
- Neurophysiology · ApplicationWhat feature allows saltatory conduction in myelinated nerves?
- Neurophysiology · ApplicationWhat ion influx causes rapid neuronal depolarization?
- Neurophysiology · ApplicationWhat prevents an immediate second action potential in a neuron?
- Neurophysiology · ApplicationWhich ion influx is primarily responsible for the rapid depolarization phase of a typical neuronal action potential?
- Neurophysiology · ApplicationWhich neurotransmitter is released at the skeletal neuromuscular junction?
- Neurophysiology · ApplicationWhich component of a simple reflex arc carries information from a receptor toward the central nervous system?
- Neurophysiology: neuromuscular junction · ApplicationBotulinum toxin causes flaccid paralysis by preventing presynaptic release of which neurotransmitter?
- Neurophysiology: muscle spindle · ApplicationStretch of a skeletal muscle activates which receptor that mediates the monosynaptic stretch reflex?
Renal physiology35
- Renal physiology · ApplicationWhich substance is freely filtered and neither reabsorbed nor secreted, so that its clearance equals GFR?
- Renal physiology · ApplicationWhich of the following favours glomerular filtration?
- Renal physiology · ApplicationWhere is the largest fraction of filtered sodium reabsorbed?
- Renal physiology: Starling forces · ApplicationA patient with nephrotic syndrome develops generalised oedema. Which Starling force change is the principal explanation?
- Renal physiology: tubuloglomerular feedback · ApplicationWhen sodium chloride delivery to the distal tubule rises, what does the macula densa do to restore the glomerular filtration rate towards normal?
- Renal physiology: proximal tubule · Multi-stepMicropuncture of the end of the proximal convoluted tubule shows that about two-thirds of filtered sodium and water is gone, glucose and amino acids are absent, yet the…
- Renal physiology · ApplicationWhat hormone increases water reabsorption in collecting ducts?
- Renal physiology · ApplicationWhat is the main process that creates glomerular filtrate?
- Renal physiology · ApplicationWhich hormone promotes sodium reabsorption in the distal nephron?
- Renal physiology · ApplicationWhat segment reabsorbs the greatest amount of filtered sodium and water?
- Renal physiology · ApplicationWhat substance is used clinically as a marker of glomerular filtration in routine practice?
- Renal physiology · ApplicationWhat is the role of renin in the renin-angiotensin system?
- Renal physiology · ApplicationWhat is the usual effect of antidiuretic hormone on urine concentration?
- Renal physiology · ApplicationWhat process returns filtered glucose to blood in the proximal tubule?
- Renal physiology · ApplicationWhat hormone is produced by kidney cells in response to hypoxia?
- Renal physiology · ApplicationWhat substance is the ideal experimental marker of glomerular filtration rate?
- Renal physiology · ApplicationWhat process creates glomerular filtrate?
- Renal physiology · ApplicationWhat hormone promotes distal sodium reabsorption?
- Renal physiology · ApplicationWhere does glomerular filtration normally occur?
- Renal physiology · ApplicationWhat is the principal renal effect of antidiuretic hormone?
- Renal physiology · ApplicationWhich action is directly promoted by aldosterone in the distal nephron?
- Renal physiology · ApplicationWhich nephron segment is largely impermeable to water while reabsorbing sodium chloride?
- Renal physiology · ApplicationWhat is the principal effect of antidiuretic hormone on the collecting duct?
- Renal physiology · ApplicationWhich change causes an increase in glomerular filtration rate at the afferent arteriole?
- Renal physiology: clearance · ApplicationA substance is freely filtered and neither reabsorbed nor secreted. Its renal clearance equals what?
- Renal physiology: tubuloglomerular feedback · Multi-stepHigh sodium chloride delivery to the macula densa causes which local response?
- Renal physiology: ADH · ApplicationAntidiuretic hormone increases water permeability of collecting ducts by inserting which channel into principal-cell apical membranes?
- Renal physiology: acid-base · ApplicationWhich nephron cell type secretes hydrogen ions and generates new bicarbonate during chronic metabolic acidosis?
- Renal physiology · ApplicationWhat is the main function of the proximal tubule?
- Renal physiology · ApplicationWhat stimulates renin release from juxtaglomerular cells?
- Renal physiology · ApplicationWhat is the effect of aldosterone in the distal nephron?
- Renal physiology: glomerular filtration · ApplicationConstriction of which arteriole initially increases glomerular capillary hydrostatic pressure and may increase GFR?
- Renal physiology: countercurrent mechanism · ApplicationWhat is the primary role of the loop of Henle in urine concentration?
- Renal physiology: ADH · ApplicationHow does antidiuretic hormone increase water reabsorption in the collecting duct?
- Renal physiology: acid-base handling · ApplicationWhich nephron segment secretes the largest fraction of filtered bicarbonate back into the blood through reabsorption?
Neurophysiology and special senses32
- Neurophysiology and special senses: spinal shock · ApplicationAfter acute complete transection of the cord at T6, the legs are flaccid with absent reflexes for several days. What mainly causes this initial areflexia?
- Neurophysiology and special senses: pupillary light reflex · Multi-stepA man with tabes dorsalis has small irregular pupils that constrict on accommodation but not to light. Where is the lesion that explains this?
- Neurophysiology and special senses: limbic system · Multi-stepAfter bilateral anterior temporal lobe resection, a monkey becomes placid, puts objects in its mouth and shows hypersexual behaviour. Which structure's loss mainly expl…
- Neurophysiology and special senses: pain transmission · ApplicationIn the dorsal horn, which neurotransmitters are released by primary nociceptive afferents onto second-order neurons?
- Neurophysiology and special senses: cochlear amplification · ApplicationA newborn hearing screen detects faint sounds emitted from the ear canal after a click. Which structure generates these otoacoustic emissions?
- Neurophysiology and special senses: Horner syndrome · ApplicationA smoker has miosis, mild ptosis and absence of sweating on the left side of the face, and a left apical lung mass. Which pathway has been interrupted?
- Neurophysiology and special senses: Papez circuit · ApplicationWhich sequence correctly describes the circuit of Papez, which is concerned with memory and emotion?
- Neurophysiology and special senses: split-brain syndrome · Multi-stepAfter section of the corpus callosum for epilepsy, a patient can name an object placed in the right hand but cannot name one in the left hand, though he can pick it out…
- Neurophysiology and special senses: Huntington disease pathway · Multi-stepA 42-year-old man has choreiform movements and cognitive decline, with atrophy of the caudate nucleus on imaging. Which basal ganglia change underlies the chorea?
- Neurophysiology and special senses: visual field defect · ApplicationA patient with a pituitary adenoma has progressive loss of the outer halves of both visual fields. Which fibres are compressed?
- Neurophysiology and special senses: visual acuity at the fovea · ApplicationVisual acuity is highest at the fovea centralis. Which feature chiefly contributes to this?
- Neurophysiology and special senses: hemispatial neglect · Multi-stepAfter a right parietal stroke, a man ignores the left side of space, leaving food on the left of his plate and shaving only the right side of his face. Visual fields ar…
- Neurophysiology and special senses: receptive aphasia · ApplicationAfter a left temporal stroke, a 66-year-old man speaks fluently, but his sentences contain made-up words and make little sense. He cannot follow simple commands and see…
- Neurophysiology and special senses: narcolepsy · ApplicationA 19-year-old has irresistible daytime sleep attacks, sudden loss of muscle tone when laughing and hallucinations on falling asleep. Cerebrospinal fluid levels of a pep…
- Neurophysiology and special senses: slow-wave sleep · ApplicationA 7-year-old child sleepwalks about an hour after falling asleep, is hard to rouse and cannot recall any dream. Which EEG activity would be predominant at that time?
- Neurophysiology and special senses: light-near dissociation · Multi-stepA patient with tertiary neurosyphilis has small irregular pupils that do not constrict to light but do constrict when focusing on a near object. Where is the lesion mos…
- Neurophysiology and special senses: aqueous humour · ApplicationA patient with raised intraocular pressure is given acetazolamide. It reduces aqueous humour formation in the ciliary epithelium by inhibiting which enzyme?
- Neurophysiology and special senses: hair cell transduction · Multi-stepWhen the stereocilia of an inner hair cell bend towards the tallest row, the cell depolarises. Which ion carries the inward current, and why is that notable?
- Neurophysiology and special senses: gate control of pain · ApplicationA child rubs the skin over a bumped knee and the pain eases. Which mechanism best explains this relief?
- Neurophysiology and special senses: midline cerebellar lesion · ApplicationA 5-year-old child with a midline posterior fossa tumour sways on standing and walks with a wide base, but finger-to-nose testing is normal. Which part of the cerebellu…
- Neurophysiology and special senses: subthalamic nucleus · Multi-stepA 70-year-old man has sudden violent flinging movements of the right arm and leg after a small lacunar infarct. Which structure is most likely involved?
- Neurophysiology and special senses: vestibular hair cell response · ApplicationIn a semicircular canal, what happens when the stereocilia of a hair cell bend towards the kinocilium?
- Neurophysiology and special senses: optic chiasm lesion · ApplicationA 35-year-old woman with galactorrhoea has bitemporal hemianopia. Which fibres are interrupted?
- Neurophysiology and special senses: acoustic reflex · Multi-stepA woman with right facial nerve palsy finds ordinary sounds uncomfortably loud in the right ear. What explains this?
- Neurophysiology and special senses: middle ear impedance matching · ApplicationSound passing from air to cochlear fluid would mostly be reflected if it were not for the middle ear. Which feature chiefly overcomes this mismatch?
- Neurophysiology and special senses: frontal eye field · Multi-stepA patient has an acute infarct of the left frontal eye field. Towards which side do the eyes deviate acutely?
- Neurophysiology and special senses: capsaicin and pain · ApplicationTopical capsaicin cream is used for post-herpetic neuralgia. Which receptor on nociceptive C fibres does it activate, eventually depleting substance P?
- Neurophysiology and special senses: cortical sensory processing · Multi-stepA man with a right parietal lesion can feel touch and vibration in his left hand but cannot identify a key placed in it with his eyes closed. Which function is impaired?
- Neurophysiology and special senses: descending pain modulation · ApplicationWhich brainstem nucleus releases serotonin in the descending pathway that activates enkephalin interneurons to inhibit dorsal horn pain transmission?
- Neurophysiology and special senses: reward pathway · ApplicationAddictive drugs increase dopamine release in which part of the reward circuit, and from which neurons does it arise?
- Neurophysiology and special senses: sound localisation · ApplicationWhich brainstem structure first compares input from the two ears to localise a sound using small differences in timing and intensity?
- Neurophysiology and special senses: cerebellar laterality · Multi-stepA patient has an infarct of the right cerebellar hemisphere. Limb ataxia appears on which side, and why?
Endocrine physiology30
- Endocrine physiology: thyroid · ApplicationA patient with thyrotoxicosis is given a large dose of iodide before surgery, and thyroid hormone synthesis and release fall transiently. What is this effect called?
- Endocrine physiology: growth hormone · ApplicationA man has coarse facial features and enlarged hands. In a healthy person an oral glucose load lowers serum growth hormone. In this patient, which result would support a…
- Endocrine physiology · ApplicationWhich hormone lowers blood glucose after a meal?
- Endocrine physiology · ApplicationWhich gland secretes thyroid-stimulating hormone?
- Endocrine physiology · ApplicationWhat is the principal effect of parathyroid hormone on serum calcium?
- Endocrine physiology · ApplicationWhat is the primary effect of glucagon on liver metabolism?
- Endocrine physiology · ApplicationWhich hormone increases serum calcium by promoting bone resorption and renal conservation?
- Endocrine physiology · ApplicationWhat is cortisol's major role during stress?
- Endocrine physiology · ApplicationWhat hormone stimulates thyroid hormone synthesis and release?
- Endocrine physiology · ApplicationWhat is the principal action of aldosterone?
- Endocrine physiology · ApplicationWhat hormone is released from the posterior pituitary to promote uterine contractions?
- Endocrine physiology · ApplicationWhich hormone promotes hepatic glycogen breakdown during fasting?
- Endocrine physiology · ApplicationWhich hormone is released from the posterior pituitary during water deprivation?
- Endocrine physiology · ApplicationWhat is the main effect of parathyroid hormone on serum calcium?
- Endocrine physiology · ApplicationWhich pancreatic cell type secretes insulin?
- Endocrine physiology · ApplicationWhat is the major acute effect of glucagon on the liver during fasting?
- Endocrine physiology · ApplicationWhat is the main immediate effect of parathyroid hormone on serum calcium homeostasis?
- Endocrine physiology · ApplicationWhich hormone is released in a surge to trigger ovulation in a typical menstrual cycle?
- Endocrine physiology · ApplicationWhy does thyroid hormone increase basal metabolic rate in many tissues?
- Endocrine physiology · ApplicationWhich endocrine feedback pattern is typical of primary adrenal failure?
- Endocrine physiology · ApplicationWhat is the key metabolic effect of insulin after a carbohydrate-rich meal?
- Endocrine physiology: insulin · ApplicationInsulin promotes uptake of glucose into skeletal muscle chiefly by translocating which transporter to the cell membrane?
- Endocrine physiology: cortisol · ApplicationCortisol increases blood glucose during stress primarily by which hepatic effect?
- Endocrine physiology: thyroid hormones · ApplicationThyroid hormone increases basal metabolic rate largely by increasing expression of what?
- Endocrine physiology: calcium · ApplicationParathyroid hormone raises serum calcium by which renal action?
- Endocrine physiology · ApplicationWhat is the major physiological action of parathyroid hormone?
- Endocrine physiology · ApplicationWhat is the main effect of glucagon on liver metabolism?
- Endocrine physiology: insulin · ApplicationIn skeletal muscle, insulin increases glucose uptake primarily by which mechanism?
- Endocrine physiology: cortisol · ApplicationWhich effect is characteristic of cortisol?
- Endocrine physiology: parathyroid hormone · ApplicationWhat is the net effect of parathyroid hormone on serum calcium and phosphate?
Cardiovascular system29
- Cardiovascular system: constrictive pericarditis · Multi-stepA 45-year-old with previous tuberculous pericarditis has ascites, a raised jugular pressure, clear lungs and a pericardial knock. Right atrial pressure tracing shows a…
- Cardiovascular system: right ventricular infarction · Multi-stepA man with an inferior wall myocardial infarction becomes hypotensive with a raised jugular venous pressure and clear lung fields. Sublingual nitrates drop his blood pr…
- Cardiovascular system: digoxin effect on ECG · ApplicationA 70-year-old with heart failure on long-term digoxin has an ECG showing downsloping, scooped ST segment depression in the lateral leads. What does this represent?
- Cardiovascular system: isometric exercise · Multi-stepA subject squeezes a handgrip dynamometer at 30 percent of maximal force for three minutes. Compared with running on a treadmill, which change is more pronounced?
- Cardiovascular system: renal artery stenosis · Multi-stepA 60-year-old with resistant hypertension and an abdominal bruit develops acute kidney injury within days of starting an ACE inhibitor. Imaging shows bilateral renal ar…
- Cardiovascular system: Poiseuille law · ApplicationAtherosclerosis narrows a femoral artery to half its original radius, with all other factors constant. By what factor does resistance to flow rise?
- Cardiovascular system: Eisenmenger syndrome · Multi-stepA 25-year-old woman with an untreated large ventricular septal defect since childhood now has cyanosis and clubbing, and the murmur has become soft. Which haemodynamic…
- Cardiovascular system: Einthoven law · ApplicationOn a normal ECG, the net QRS deflection is +4 mm in lead I and +6 mm in lead III. What is the net QRS deflection in lead II?
- Cardiovascular system: jugular venous pulse · Multi-stepA 70-year-old man with an irregularly irregular pulse has no visible 'a' wave in the jugular venous pulse. What is the physiological reason?
- Cardiovascular system: autonomic control of circulation · Multi-stepA 62-year-old man with diabetic autonomic neuropathy faints on standing. Blood pressure falls from 130/80 to 80/50 mmHg and his pulse does not change. Which mechanism h…
- Cardiovascular system: coronary circulation · ApplicationDuring exercise, myocardial oxygen demand rises, yet the heart cannot meet it by extracting more oxygen from each unit of blood. Why not?
- Cardiovascular system: venous return curve · Multi-stepA hypovolaemic patient receives a rapid litre of intravenous saline. On a venous return curve plotted against right atrial pressure, what change results?
- Cardiovascular system: Wenckebach conduction · ApplicationAn ECG shows PR interval lengthening on successive beats until a P wave fails to conduct, after which the cycle repeats. What conduction property underlies this pattern?
- Cardiovascular system: pulsus paradoxus mechanism · Multi-stepIn a patient with cardiac tamponade the systolic pressure falls by more than 10 mmHg during inspiration. Which mechanism contributes most to this?
- Cardiovascular system: Kussmaul sign · Multi-stepIn constrictive pericarditis the jugular venous pressure rises, instead of falling, during inspiration. What is the reason?
- Cardiovascular system: atrial contribution to ventricular filling · ApplicationA 64-year-old man with long-standing hypertension and a thick, stiff left ventricle develops atrial fibrillation. His ventricular rate is controlled at 80 per minute, y…
- Cardiovascular system: ECG in hypocalcaemia · ApplicationA woman develops perioral tingling and carpopedal spasm two days after total thyroidectomy. Which ECG finding is expected?
- Cardiovascular system: neurogenic orthostatic hypotension · Multi-stepA 58-year-old man with long-standing diabetes feels faint on standing. Supine blood pressure is 140/85 mmHg and heart rate 78 per minute. After three minutes standing,…
- Cardiovascular system: transcapillary refill after haemorrhage · ApplicationA man loses 1 litre of blood from a road accident and bleeding is then controlled. Over the next 24 hours his haemoglobin concentration falls further without any more b…
- Cardiovascular system: distributive shock haemodynamics · Multi-stepA 45-year-old woman with pneumonia has bounding pulses, warm flushed extremities, blood pressure 80/35 mmHg and a high cardiac output on echocardiography. Which haemody…
- Cardiovascular system: fetal blood streaming · ApplicationIn a normal late-gestation fetus, which organs receive blood with the highest oxygen content?
- Cardiovascular system: subendocardial ischaemia in aortic stenosis · Multi-stepA 66-year-old man with severe aortic stenosis and a thick left ventricle has exertional angina, although coronary angiography is normal. Which mechanism makes the inner…
- Cardiovascular system: vasovagal syncope · ApplicationA 19-year-old student becomes pale and sweaty at the sight of blood, then faints. Heart rate is 44 per minute and blood pressure 80/45 mmHg. What is the mechanism?
- Cardiovascular system: overdrive suppression of the sinus node · Multi-stepAn atrial tachycardia at 180 per minute stops abruptly in a patient with sinus node disease, and there is a pause of about three seconds before the first sinus beat. Wh…
- Cardiovascular system: shift of cerebral autoregulation in hypertension · Multi-stepA 58-year-old man with poorly controlled hypertension has his blood pressure reduced from 220/120 to 110/70 mmHg within an hour, and he becomes confused with a transien…
- Cardiovascular system: haemodynamic profile of cardiogenic shock · ApplicationA 62-year-old man with an extensive anterior myocardial infarction is cold, clammy and breathless with blood pressure 78/50 mmHg and bibasal crepitations. Which haemody…
- Cardiovascular system: the transplanted denervated heart · ApplicationSix months after orthotopic heart transplantation, a man has a resting heart rate of 100 per minute. During exercise his rate rises slowly and it recovers slowly afterw…
- Cardiovascular system: baroreceptor resetting · Multi-stepWhy do the carotid sinus baroreceptors of a man with long-standing hypertension not lower his pressure back to normal?
- Cardiovascular system: paradoxical coronary constriction with acetylcholine · Multi-stepDuring coronary angiography, intracoronary acetylcholine dilates the arteries of a young control but constricts the arteries of a patient with advanced atherosclerosis.…
Gastrointestinal29
- Gastrointestinal: swallowing · ApplicationA 60-year-old man after a lateral medullary stroke can start a swallow voluntarily but the food is not carried through the pharynx and he aspirates. Which structure nor…
- Gastrointestinal: hepatic glucose output · ApplicationA patient with fulminant hepatic failure has recurrent hypoglycaemia despite adequate food intake. Which hepatic functions fail?
- Gastrointestinal: secretory IgA transport · ApplicationA newborn is protected against gut infections by antibody in breast milk. Which cell process delivers dimeric IgA across the mammary epithelium into the milk?
- Gastrointestinal: gastric acid and PPI action · Multi-stepA 40-year-old with a duodenal ulcer is started on omeprazole. Compared with an H2 blocker, why is acid suppression more complete, including after meals?
- Gastrointestinal: carbohydrate malabsorption · ApplicationAn infant has explosive watery stools with acidic pH after milk feeds, and the stool contains reducing substances. Which mechanism explains the diarrhoea?
- Gastrointestinal: Brunner's glands · ApplicationWhich structures in the duodenal submucosa secrete a viscous alkaline mucus to protect the duodenal mucosa from acid chyme, and are stimulated by vagal activity and sec…
- Gastrointestinal: alkaline tide · ApplicationAfter a large meal, venous blood draining the stomach is more alkaline than arterial blood. What is the mechanism?
- Gastrointestinal: ileocaecal valve · ApplicationA patient who has had the ileocaecal valve resected develops diarrhoea with bacterial overgrowth of the distal small bowel. Which normal function of the valve has been…
- Gastrointestinal: cholestatic coagulopathy · ApplicationA patient with complete obstruction of the common bile duct has pale stools and easy bruising with a prolonged prothrombin time. What is the mechanism of the coagulopat…
- Gastrointestinal: ileal brake · Multi-stepWhen unabsorbed fat reaches the distal ileum, gastric emptying and small bowel transit slow down. Which gut peptides mediate this feedback?
- Gastrointestinal: pancreatic exocrine reserve and steatorrhoea · ApplicationA 52-year-old man with chronic alcoholic pancreatitis loses pancreatic exocrine function gradually. Which digestive abnormality appears first and is most prominent?
- Gastrointestinal: cystic fibrosis and pancreatic secretion · ApplicationA 4-year-old boy with recurrent chest infections has bulky, greasy, foul-smelling stools and poor weight gain. Which pancreatic abnormality causes the malabsorption?
- Gastrointestinal: bile acid diarrhoea · Multi-stepA man with Crohn's disease has had 40 cm of terminal ileum resected. He now has watery diarrhoea without marked steatorrhoea, which improves with cholestyramine. Which…
- Gastrointestinal: concentration of bile in the gallbladder · ApplicationHepatic bile is concentrated five- to tenfold in the gallbladder between meals while remaining isosmotic with plasma. What drives this concentration?
- Gastrointestinal: serotonin and chemotherapy-induced vomiting · ApplicationA patient receiving cisplatin develops severe vomiting within a few hours, which is largely prevented by ondansetron. Which cells release the mediator that triggers the…
- Gastrointestinal: hepatic zonation and ischaemia · Multi-stepA patient who survived prolonged hypotension has liver biopsy showing necrosis of hepatocytes around the central veins, with sparing of the periportal cells. Why are th…
- Gastrointestinal: hepatic encephalopathy and ammonia · ApplicationA 55-year-old man with cirrhosis becomes confused after an upper gastrointestinal bleed, and his arterial ammonia is raised. Which physiological failure mainly explains…
- Gastrointestinal: intestinal calcium absorption · ApplicationA child with vitamin D deficiency has rickets and low serum calcium. Which process of calcium absorption is most impaired?
- Gastrointestinal: heartburn in pregnancy · ApplicationA woman in the third trimester of pregnancy has frequent heartburn on lying down. Which hormonal effect contributes most to her symptoms?
- Gastrointestinal: paralytic ileus · ApplicationOn the second day after major abdominal surgery, a patient has abdominal distension, absent bowel sounds and no flatus. Which physiological mechanism contributes to thi…
- Gastrointestinal: rectoanal inhibitory reflex · ApplicationA newborn has delayed passage of meconium and a contracted distal segment on contrast enema. Anorectal manometry shows that rectal distension no longer causes the inter…
- Gastrointestinal: cephalic phase of gastric secretion · ApplicationA patient with an oesophageal obstruction chews food and spits it out, and gastric acid secretion still rises. Which pathway is responsible?
- Gastrointestinal: abetalipoproteinaemia · Multi-stepA child with steatorrhoea, acanthocytes and absent serum chylomicrons and LDL has a biopsy in which the enterocytes are filled with fat droplets. What is the defect?
- Gastrointestinal: D-xylose absorption test · Multi-stepIn a patient with chronic diarrhoea and steatorrhoea, the oral D-xylose absorption test is abnormal. What does this indicate?
- Gastrointestinal: hepatic arterial buffer response · Multi-stepIn a patient with portal vein thrombosis, hepatic arterial flow increases. What is the mechanism?
- Gastrointestinal: Crigler-Najjar syndrome · ApplicationA newborn develops severe unconjugated hyperbilirubinaemia with neurological signs in the first week. The bilirubin does not fall with phenobarbital. What is the defect?
- Gastrointestinal: autoimmune gastritis · Multi-stepA 55-year-old woman has megaloblastic anaemia, achlorhydria and antiparietal cell antibodies. Which pattern of gastric markers is expected?
- Gastrointestinal: adaptation after small bowel resection · ApplicationAfter extensive small bowel resection, the remaining intestine gradually increases villus height and crypt depth. Which peptide is a main trophic mediator of this adapt…
- Gastrointestinal: fat digestion after cholecystectomy · ApplicationWhy do most patients digest fat adequately after cholecystectomy?
Renal and acid–base28
- Renal and acid–base: obstructive uropathy · ApplicationA 35-year-old with an impacted ureteric calculus has renal colic and falling urine output. Which change in the Starling forces of the glomerulus explains the fall in GFR?
- Renal and acid–base: neurogenic bladder · Multi-stepA woman with a prolapsed lumbar disc has saddle anaesthesia and a painless distended bladder with continuous dribbling. Which reflex arc is interrupted?
- Renal and acid–base: renal erythropoietin · ApplicationA 50-year-old with chronic kidney disease has normocytic anaemia with low reticulocytes and normal iron stores. Which cells have lost the capacity to produce the releva…
- Renal and acid–base: renal ammonium excretion · ApplicationA patient with chronic metabolic acidosis from kidney disease excretes more acid over several days without a change in urinary pH. Which adaptation provides most of the…
- Renal and acid–base: glomerular haemodynamics · Multi-stepIn a patient with early renal artery stenosis, angiotensin II constricts the efferent arteriole more than the afferent arteriole. What happens to GFR, renal plasma flow…
- Renal and acid–base: urinary indices in prerenal azotaemia · ApplicationA 30-year-old man has had severe vomiting and diarrhoea for 3 days. His serum creatinine is raised, but his urine sediment is bland. Which urinary finding favours a pre…
- Renal and acid–base: urea handling and the BUN to creatinine ratio · Multi-stepA dehydrated patient has a raised blood urea nitrogen to creatinine ratio, although the GFR has fallen only moderately. Which difference in renal handling explains the…
- Renal and acid–base: creatinine secretion and trimethoprim · Multi-stepA patient with a urinary tract infection takes co-trimoxazole. Serum creatinine rises from 0.9 to 1.2 mg/dL, but serum cystatin C and the urine output are unchanged and…
- Renal and acid–base: lithium and nephrogenic diabetes insipidus · ApplicationA 40-year-old woman on long-term lithium therapy for bipolar disorder passes large volumes of dilute urine, and her urine osmolality barely rises after desmopressin. Wh…
- Renal and acid–base: osmotic diuresis · ApplicationA man with uncontrolled diabetes mellitus has polyuria and glycosuria, and his plasma glucose is 450 mg/dL. Which mechanism accounts for the polyuria?
- Renal and acid–base: magnesium and calcium handling in the thick ascending limb · ApplicationA patient on long-term high-dose furosemide has increased urinary magnesium and calcium excretion. Which mechanism explains this?
- Renal and acid–base: bladder storage phase · ApplicationDuring the storage phase of the bladder, sympathetic activity through the hypogastric nerve (T10 to L2) helps continence. Which combination of effects does it produce?
- Renal and acid–base: proximal tubule water reabsorption · ApplicationIn micropuncture studies, the tubular fluid to plasma inulin concentration ratio (TF/P inulin) at the end of the proximal tubule is 3. What fraction of the filtered wat…
- Renal and acid–base: type 4 renal tubular acidosis · Multi-stepA 62-year-old man with long-standing diabetic nephropathy has serum potassium 6.2 mmol/L, bicarbonate 17 mmol/L, a normal anion gap and urine pH of 5.0. Plasma renin an…
- Renal and acid–base: salicylate poisoning · Multi-stepA 24-year-old woman who took a large number of aspirin tablets has tinnitus, rapid deep breathing and sweating. Arterial blood shows pH 7.46, PaCO2 20 mmHg and bicarbon…
- Renal and acid–base: urine chloride in metabolic alkalosis · Multi-stepA 25-year-old woman has normal blood pressure, a serum potassium of 2.8 mmol/L and metabolic alkalosis. A urine diuretic screen is negative, and urinary chloride is ver…
- Renal and acid–base: primary polydipsia · ApplicationA 35-year-old woman with schizophrenia drinks about 10 litres of water daily. Her serum sodium is 124 mmol/L and urine osmolality is 60 mOsm/kg. What is the best explan…
- Renal and acid–base: potassium in diabetic ketoacidosis · ApplicationA patient in diabetic ketoacidosis has a serum potassium of 5.6 mmol/L on arrival, though total body potassium is depleted from osmotic diuresis. After starting insulin…
- Renal and acid–base: renal medullary hypoxia · Multi-stepAfter prolonged hypotension, which tubular segment is most vulnerable to ischaemic injury?
- Renal and acid–base: NSAID plus ACE inhibitor in volume depletion · Multi-stepA 70-year-old man with diarrhoea who takes an ACE inhibitor and ibuprofen develops acute kidney injury. Which combination of effects on glomerular arterioles explains t…
- Renal and acid–base: charge barrier in nephrotic syndrome · ApplicationA 5-year-old boy has heavy proteinuria, mostly albumin, and generalised oedema. Light microscopy of the glomeruli is normal. Which physiological defect underlies the pr…
- Renal and acid–base: osmotic diuresis with mannitol · ApplicationA patient with raised intracranial pressure is given intravenous mannitol and urine volume rises sharply. What is the renal mechanism?
- Renal and acid–base: volume versus osmotic control of ADH · Multi-stepA patient with severe haemorrhage and a low serum osmolality continues to release ADH. Which statement best explains this?
- Renal and acid–base: potassium shift in mineral acidosis · Multi-stepWhy does hyperkalaemia occur more readily in a metabolic acidosis due to hydrochloric acid loading than in lactic acidosis?
- Renal and acid–base: vulnerability of the outer medulla · ApplicationWhich feature makes the thick ascending limb in the outer medulla especially vulnerable to acute tubular injury during hypotension?
- Renal and acid–base: glomerulotubular balance · ApplicationIn a healthy kidney, when the GFR rises moderately, the proximal tubule absorbs a larger absolute amount of sodium and water. What is this phenomenon called and what do…
- Renal and acid–base: alkalosis and hypokalaemia in primary aldosteronism · ApplicationA woman with an aldosterone-secreting adenoma has hypertension, hypokalaemia and a mild metabolic alkalosis. Which tubular mechanism accounts for the potassium and hydr…
- Renal and acid–base: potassium loss in persistent vomiting · Multi-stepA man with prolonged vomiting has metabolic alkalosis, volume depletion and a low serum potassium, with a high urinary potassium. Which mechanism contributes most to th…
Respiratory physiology28
- Respiratory physiology: ventilation-perfusion · ApplicationIn an upright healthy adult, which statement about regional lung ventilation and perfusion is correct?
- Respiratory physiology: surfactant · ApplicationA premature neonate has grunting respiration and a ground-glass chest radiograph. Which physiological change is primarily responsible for the impaired lung mechanics?
- Respiratory physiology: altitude · Multi-stepA healthy lowlander ascends rapidly to 4500 m. After one week of acclimatisation, which combination is expected?
- Respiratory physiology: alveolar ventilation · ApplicationA resting adult breathes with a tidal volume of 500 mL at 12 breaths per minute. Anatomical dead space is 150 mL. What is the alveolar ventilation?
- Respiratory physiology: oxygen content · ApplicationA healthy adult has a haemoglobin of 15 g/dL and an arterial oxygen saturation of 100%. Ignoring dissolved oxygen, what is the approximate oxygen content of arterial bl…
- Respiratory physiology · ApplicationWhat is the primary stimulus for ventilation in healthy adults?
- Respiratory physiology · ApplicationWhere does most gas exchange occur in the lungs?
- Respiratory physiology · ApplicationWhat is the main form in which carbon dioxide is transported in blood?
- Respiratory physiology · ApplicationWhat changes during exercise to enhance oxygen delivery?
- Respiratory physiology · ApplicationWhat is surfactant's principal action in alveoli?
- Respiratory physiology · ApplicationWhat muscle is the main driver of quiet inspiration?
- Respiratory physiology · ApplicationWhat is tidal volume?
- Respiratory physiology · ApplicationWhat mechanism matches perfusion to ventilation in the lung?
- Respiratory physiology · ApplicationWhat is the main drive to ventilation in healthy adults?
- Respiratory physiology · ApplicationWhere does most pulmonary gas exchange occur?
- Respiratory physiology · ApplicationWhat does a ventilation-perfusion ratio describe in the lung?
- Respiratory physiology · ApplicationWhich change shifts the oxyhaemoglobin dissociation curve to the right and facilitates tissue oxygen unloading?
- Respiratory physiology · ApplicationWhat is the main role of pulmonary surfactant?
- Respiratory physiology · ApplicationWhat happens to oxygen partial pressure as inspired air reaches humidified alveoli?
- Respiratory physiology · ApplicationWhich factor shifts the oxyhaemoglobin dissociation curve to the right?
- Respiratory physiology: compliance · ApplicationPulmonary surfactant increases lung compliance chiefly by doing what?
- Respiratory physiology: oxygen dissociation curve · ApplicationWhich change shifts the oxyhaemoglobin dissociation curve to the right?
- Respiratory physiology: V/Q mismatch · Multi-stepA pulmonary embolus produces alveoli that are ventilated but poorly perfused. This region has which ventilation-perfusion relationship?
- Respiratory physiology · ApplicationWhat is functional residual capacity?
- Respiratory physiology · ApplicationWhy does carbon monoxide poisoning impair oxygen delivery?
- Respiratory physiology: compliance · ApplicationWhich condition is associated with increased lung compliance?
- Respiratory physiology: V/Q mismatch · ApplicationWhich region of an upright normal lung has the highest ventilation-perfusion ratio?
- Respiratory physiology: oxygen dissociation curve · ApplicationWhich change shifts the oxyhemoglobin dissociation curve to the right?
Gastrointestinal physiology27
- Gastrointestinal physiology: gastric acid · ApplicationWhich agent stimulates gastric acid secretion by acting directly on the parietal cell through a G-protein coupled receptor that raises intracellular calcium?
- Gastrointestinal physiology: bile salts · ApplicationA patient after ileal resection has steatorrhoea and gallstones. Which physiological mechanism explains these findings?
- Gastrointestinal physiology: Helicobacter pylori and gastrin · Multi-stepA 40-year-old man with duodenal ulcer has antral-predominant Helicobacter pylori infection, a raised fasting gastrin and high acid output. A secretin stimulation test d…
- Gastrointestinal physiology: enteropeptidase · Multi-stepAn infant has failure to thrive, diarrhoea and hypoproteinaemic oedema from weaning. Duodenal fluid has trypsinogen but almost no trypsin or chymotrypsin activity, and…
- Gastrointestinal physiology: medium-chain triglycerides · ApplicationA 9-month-old with biliary atresia after a Kasai procedure has steatorrhoea and poor weight gain. A formula rich in medium-chain triglycerides is introduced. Why does t…
- Gastrointestinal physiology: conjugated hyperbilirubinaemia · Multi-stepA 20-year-old has mild recurrent jaundice with total bilirubin 4 mg/dL, more than half conjugated, dark urine, and normal ALT and alkaline phosphatase. Liver biopsy sho…
- Gastrointestinal physiology: effects of truncal vagotomy · Multi-stepAfter truncal vagotomy without a drainage procedure, a patient has early satiety and postprandial fullness, with retention of solid food, while liquids empty rapidly. W…
- Gastrointestinal physiology: short-chain fatty acids · ApplicationA patient with a defunctioned colon segment after ileostomy develops diversion colitis that improves with short-chain fatty acid enemas. Which short-chain fatty acid is…
- Gastrointestinal physiology: villus countercurrent exchange · Multi-stepA 70-year-old man with atrial fibrillation has acute abdominal pain from low mesenteric blood flow. Mucosal necrosis starts at the villus tips. What explains this early…
- Gastrointestinal physiology · ApplicationWhich cells secrete hydrochloric acid in the stomach?
- Gastrointestinal physiology · ApplicationWhat enzyme begins protein digestion in the stomach?
- Gastrointestinal physiology · ApplicationWhat hormone stimulates gallbladder contraction after a fatty meal?
- Gastrointestinal physiology · ApplicationWhere is most nutrient absorption completed?
- Gastrointestinal physiology · ApplicationWhat is the main action of secretin?
- Gastrointestinal physiology · ApplicationWhat is the primary role of bile salts?
- Gastrointestinal physiology · ApplicationWhich stomach cells secrete hydrochloric acid?
- Gastrointestinal physiology · ApplicationWhat transporter mediates fructose uptake at the intestinal brush border?
- Gastrointestinal physiology · ApplicationWhich gastric cell type secretes hydrochloric acid?
- Gastrointestinal physiology · ApplicationWhat is a key digestive function of bile salts?
- Gastrointestinal physiology · ApplicationWhich hormone stimulates pancreatic bicarbonate secretion after acid enters duodenum?
- Gastrointestinal physiology · ApplicationWhat is the main action of cholecystokinin after a fatty meal?
- Gastrointestinal physiology: gastric acid · ApplicationWhich signal directly stimulates parietal cells to secrete hydrochloric acid through H2 receptors?
- Gastrointestinal physiology: pancreatic secretion · ApplicationAcidic chyme entering the duodenum causes S cells to release which hormone that stimulates pancreatic bicarbonate secretion?
- Gastrointestinal physiology · ApplicationWhat is the principal role of intrinsic factor?
- Gastrointestinal physiology · ApplicationWhat triggers release of gastrin?
- Gastrointestinal physiology: gastric secretion · ApplicationWhich cell secretes intrinsic factor in the stomach?
- Gastrointestinal physiology: pancreatic secretion · ApplicationWhich hormone stimulates bicarbonate-rich pancreatic secretion in response to acidic chyme entering the duodenum?
Muscle physiology24
- Muscle physiology · ApplicationIn skeletal muscle excitation–contraction coupling, calcium released from the sarcoplasmic reticulum binds to which protein?
- Muscle physiology: smooth muscle · ApplicationIn smooth muscle, how does a rise in intracellular calcium produce contraction?
- Muscle physiology: length-tension relation · Multi-stepIn an isolated skeletal muscle experiment, the muscle is progressively stretched before stimulation. Active force is greatest at a sarcomere length of about 2.2 microme…
- Muscle physiology: Golgi tendon organ · ApplicationA man with an upper motor neurone lesion has a limb that resists passive stretch strongly and then suddenly gives way, the clasp-knife phenomenon. Which receptor mechan…
- Muscle physiology: malignant hyperthermia · ApplicationA 22-year-old man undergoing general anaesthesia with halothane and succinylcholine develops muscle rigidity, tachycardia, rising end-tidal carbon dioxide and a tempera…
- Muscle physiology: energy metabolism · Multi-stepA 19-year-old man has painful cramps and dark urine after sprinting but feels better after a brief rest (second wind). In an ischaemic forearm exercise test, venous amm…
- Muscle physiology: motor unit recruitment · ApplicationA person gradually increases the force of voluntary contraction of the biceps from a very light grip to a maximal effort. Which sequence of motor unit recruitment occurs?
- Muscle physiology: summation and tetanus · ApplicationWhen a skeletal muscle is stimulated repetitively at a high frequency, it develops a smooth sustained contraction with greater force than a single twitch. What is the m…
- Muscle physiology: denervation · Multi-stepA 45-year-old man with a lumbar radiculopathy has had weakness of ankle dorsiflexion for six weeks. Needle electromyography at rest shows spontaneous fibrillation poten…
- Muscle physiology: force-velocity relation · ApplicationIn an isolated skeletal muscle lifting different loads, shortening velocity falls as the load increases. At what load is mechanical power output (force x velocity) grea…
- Muscle physiology: muscle spindle dynamic response · ApplicationA reflex hammer strikes the patellar tendon, causing a brief rapid stretch of the quadriceps. Which receptor generates the largest burst of discharge during the changin…
- Muscle physiology: excitation-contraction coupling in skeletal versus cardiac muscle · ApplicationStrips of skeletal and ventricular muscle are placed in a calcium-free solution containing a chelator and stimulated electrically. What is observed?
- Muscle physiology: thyrotoxic periodic paralysis · Multi-stepA 28-year-old man wakes with sudden flaccid weakness of both legs after a heavy carbohydrate meal the night before. He has tremor, tachycardia and a goitre; serum potas…
- Muscle physiology: electromyography in myopathy · Multi-stepA 10-year-old boy with proximal muscle weakness and a very high creatine kinase has needle electromyography showing small, short, polyphasic motor unit potentials with…
- Muscle physiology · ApplicationWhat ion binds troponin to initiate skeletal muscle contraction?
- Muscle physiology · ApplicationWhat provides the immediate energy for cross-bridge cycling?
- Muscle physiology · ApplicationWhat is the functional contractile unit of skeletal muscle?
- Muscle physiology · ApplicationWhat occurs during the latent period of a muscle twitch?
- Muscle physiology · ApplicationWhat is the effect of increased preload on stroke volume within normal limits?
- Muscle physiology · ApplicationWhat ion binds troponin to initiate skeletal contraction?
- Muscle physiology · ApplicationWhat event allows myosin to bind actin in skeletal muscle contraction?
- Muscle physiology · ApplicationWhat directly binds calcium to initiate skeletal muscle contraction?
- Muscle physiology · ApplicationWhat causes rigor mortis after death?
- Muscle physiology: excitation-contraction coupling · ApplicationIn skeletal muscle, calcium binds to which protein to initiate contraction?
Renal24
- Renal: creatinine clearance · ApplicationA patient has plasma creatinine 1 mg/dL, urine creatinine 60 mg/dL and urine flow 2 mL/min. What is the creatinine clearance?
- Renal: renal blood flow · Multi-stepIn a healthy adult the clearance of para-aminohippurate (PAH) is 600 mL/min and the haematocrit is 40%. What is the approximate renal blood flow?
- Renal: autoregulation of GFR · Multi-stepA 68-year-old man with bilateral renal artery stenosis starts an ACE inhibitor and within days his creatinine rises from 1.1 to 2.4 mg/dL. What is the mechanism?
- Renal: tubular transport defects · ApplicationA 4-year-old with failure to thrive and polyuria has normal blood pressure, hypokalaemia, metabolic alkalosis and hypercalciuria. Which transporter is most likely defec…
- Renal: calcium handling and thiazides · ApplicationA 40-year-old man with recurrent calcium oxalate stones and hypercalciuria is started on hydrochlorothiazide. How does the drug reduce urinary calcium?
- Renal: aldosterone and potassium · ApplicationA 38-year-old woman has blood pressure 170/105 mmHg, serum potassium 2.9 mmol/L and bicarbonate 31 mmol/L, with low plasma renin and raised aldosterone. Which tubular e…
- Renal: urinary concentration and urea · Multi-stepA child with severe protein-energy malnutrition cannot concentrate urine maximally even though the ADH level is high and the collecting duct responds to ADH. Which mech…
- Renal: water excretion and ADH excess · ApplicationA 62-year-old smoker with small cell lung cancer is euvolaemic with serum sodium 118 mmol/L, serum osmolality 250 mOsm/kg, urine osmolality 480 mOsm/kg and urine sodium…
- Renal: glucose handling · ApplicationA diabetic patient on an SGLT2 inhibitor has glycosuria although plasma glucose is 100 mg/dL. What is the explanation?
- Renal: natriuretic peptide · ApplicationA patient in heart failure has raised atrial natriuretic peptide. Which arteriolar effect in the kidney contributes to the natriuresis?
- Renal: micturition after spinal injury · ApplicationA 30-year-old man had a complete T8 spinal cord transection 6 months ago. Initially his bladder was atonic with retention. Which describes his bladder now?
- Renal: Gitelman syndrome · Multi-stepA 24-year-old woman has muscle cramps, hypokalaemic metabolic alkalosis, hypomagnesaemia, low urinary calcium excretion and a normal-to-low blood pressure. Which transp…
- Renal: Liddle syndrome · Multi-stepA 16-year-old has hypertension, hypokalaemia and metabolic alkalosis, with low plasma renin and low aldosterone. Spironolactone does not correct the problem. Which drug…
- Renal: free water clearance · Multi-stepA patient passes 120 mL of urine per hour with urine osmolality 600 mOsm/kg. Plasma osmolality is 300 mOsm/kg. What is the free water clearance?
- Renal: renal blood flow and filtration fraction · ApplicationA man has para-aminohippurate clearance of 600 mL/min, inulin clearance of 120 mL/min and haematocrit 40%. What are his filtration fraction and renal blood flow?
- Renal: loop diuretics and concentration · ApplicationAfter several days of high-dose furosemide, a patient's urine osmolality is close to plasma osmolality at about 300 mOsm/kg regardless of hydration. What is the explana…
- Renal: calcitriol synthesis · ApplicationA 45-year-old man with advanced chronic kidney disease has hypocalcaemia and raised PTH. Which failure of renal function contributes most directly to the hypocalcaemia?
- Renal: Starling forces in glomerular filtration · Multi-stepIn a patient, glomerular capillary hydrostatic pressure is 60 mmHg, plasma oncotic pressure in the capillary is 32 mmHg and Bowman space pressure is 18 mmHg. A ureteric…
- Renal · ApplicationWhere is most filtered sodium reabsorbed?
- Renal · ApplicationWhich hormone increases collecting-duct water permeability?
- Renal · ApplicationWhat does renin cleave?
- Renal · ApplicationWhat is filtration barrier component?
- Renal · ApplicationWhat hormone increases sodium reabsorption?
- Renal · ApplicationWhat does ADH increase?
Cardiovascular physiology21
- Cardiovascular physiology: blood pressure · ApplicationA patient's blood pressure is 150/90 mmHg. Using diastolic pressure plus one-third of pulse pressure, what is the mean arterial pressure?
- Cardiovascular physiology: jugular venous pulse · ApplicationA patient with complete heart block has intermittent large, brisk waves in the neck veins. These 'cannon a waves' occur because:
- Cardiovascular physiology · ApplicationWhich structure normally acts as the heart's primary pacemaker?
- Cardiovascular physiology · ApplicationCardiac output is the product of heart rate and what?
- Cardiovascular physiology · ApplicationWhat is the major determinant of arterial blood pressure?
- Cardiovascular physiology · ApplicationWhat phase of the cardiac cycle ejects blood from the ventricles?
- Cardiovascular physiology · ApplicationWhat reflex responds to a sudden fall in arterial pressure?
- Cardiovascular physiology · ApplicationWhat factor most directly increases venous return during leg-muscle activity?
- Cardiovascular physiology · ApplicationWhat valve closes at the beginning of ventricular systole?
- Cardiovascular physiology · ApplicationWhat causes the first heart sound?
- Cardiovascular physiology · ApplicationWhat happens to systemic vascular resistance during normal dynamic exercise?
- Cardiovascular physiology · ApplicationWhat structure is the normal primary cardiac pacemaker?
- Cardiovascular physiology · ApplicationWhat are major determinants of arterial pressure?
- Cardiovascular physiology · ApplicationWhich cardiac structure normally has the highest intrinsic pacemaker rate?
- Cardiovascular physiology · ApplicationHow is cardiac output calculated?
- Cardiovascular physiology · ApplicationWhat is the immediate reflex response to a sudden fall in arterial blood pressure?
- Cardiovascular physiology · ApplicationWhat is the primary pacemaker of the normal heart?
- Cardiovascular physiology · ApplicationWhich change most directly increases cardiac output when heart rate is unchanged?
- Cardiovascular physiology · ApplicationWhat is the Frank-Starling mechanism describing?
- Cardiovascular physiology · ApplicationWhich factor most directly determines mean arterial pressure?
- Cardiovascular physiology · ApplicationWhat reflex increases heart rate after sudden arterial pressure fall?
GI physiology20
- GI physiology: salivary secretion · ApplicationA volunteer chews lemon peel and parotid saliva flow rises about fivefold. Compared with resting saliva, how does the composition change?
- GI physiology: oesophageal motility · ApplicationA 34-year-old man has dysphagia for solids and liquids, regurgitation of undigested food and weight loss. Barium swallow shows a dilated oesophagus with a smooth taperi…
- GI physiology: gastric motility · Multi-stepA 50-year-old man has had a truncal vagotomy. Which alteration of gastric emptying is expected?
- GI physiology: pancreatic enzymes · ApplicationA 3-month-old infant has diarrhoea, failure to thrive and oedema with low serum albumin. Duodenal fluid has normal trypsinogen but no trypsin activity. Which missing en…
- GI physiology: absorption of glucose and rehydration · ApplicationA 2-year-old with acute watery diarrhoea from cholera is treated with oral rehydration solution containing glucose and sodium. Why does glucose improve sodium and water…
- GI physiology: osmotic diarrhoea · Multi-stepA 17-year-old boy has bloating and watery stools after drinking milk. A stool sample has sodium 30 mmol/L and potassium 20 mmol/L, and plasma osmolality is 290 mOsm/kg.…
- GI physiology: iron absorption · Multi-stepA 45-year-old woman with rheumatoid arthritis has a hypochromic microcytic anaemia, low serum iron and high ferritin. Raised hepcidin is found. How does hepcidin reduce…
- GI physiology: bilirubin metabolism · ApplicationA 55-year-old man has painless jaundice, dark urine, pale stools and itching. A carcinoma of the head of the pancreas obstructs the common bile duct. Which urinary find…
- GI physiology: colonic function · ApplicationA patient on prolonged broad-spectrum antibiotics develops watery diarrhoea. Which colonic function loss helps to explain this?
- GI physiology: cholera toxin · ApplicationIn cholera the enterocyte secretes large volumes of chloride-rich fluid. Which sequence correctly describes the molecular action of the toxin?
- GI physiology: mucosal defence · ApplicationA 58-year-old man taking diclofenac for arthritis presents with epigastric pain and an antral ulcer. Which mechanism of mucosal damage is most directly responsible?
- GI physiology: Zollinger-Ellison syndrome · Multi-stepA 42-year-old man has recurrent duodenal and jejunal ulcers, and fatty, loose stools. Fasting gastrin is markedly raised and gastric pH is 1.5. Which mechanism best exp…
- GI physiology: protein absorption · Multi-stepAn 8-year-old child has a photosensitive pellagra-like rash and intermittent ataxia. Urine shows a large excess of neutral amino acids, yet plasma amino acid levels and…
- GI physiology: dumping syndrome · ApplicationA 48-year-old man after partial gastrectomy develops sweating, tremor and light-headedness 2 hours after a carbohydrate-rich meal, with a capillary glucose of 2.6 mmol/…
- GI physiology: appetite regulation · ApplicationA 6-year-old child with Prader-Willi syndrome has relentless hunger and obesity. Which gut hormone is characteristically elevated and acts on the arcuate nucleus to sti…
- GI physiology: incretins · ApplicationIn a healthy volunteer, an oral glucose load produces a much larger insulin response than an intravenous glucose infusion that gives the same plasma glucose curve. What…
- GI physiology: VIPoma · Multi-stepA 45-year-old woman has profuse watery diarrhoea (more than 3 L daily) that persists during a 48-hour fast, with hypokalaemia and low gastric acid output. Which hormone…
- GI physiology: defecation · ApplicationA man feels the urge to defecate during a meeting. The rectum is distended and the internal anal sphincter relaxes reflexly. What allows him to maintain continence?
- GI physiology: unconjugated hyperbilirubinaemia · ApplicationA 20-year-old man has mild jaundice during a fast and an episode of gastroenteritis. Bilirubin is 34 micromol/L, mainly unconjugated, with normal liver enzymes, haemogl…
- GI physiology: enteric nervous system · Multi-stepA newborn has not passed meconium for 48 hours and has abdominal distension. Anorectal manometry shows absence of the normal fall in internal sphincter pressure when th…
Special senses19
- Special senses: hearing · ApplicationA factory worker with long-standing noise exposure loses high-frequency hearing first. Which part of the cochlea is most affected?
- Special senses: vision · ApplicationWhat is the effect of light on the membrane of a rod photoreceptor?
- Special senses: visual pathway · Multi-stepAfter a right anterior temporal lobectomy a patient reports loss of vision in the upper left quadrant of the visual field of both eyes. Which fibres have been interrupt…
- Special senses: dark adaptation · ApplicationA malnourished child in a rural area has Bitot spots and cannot see in dim light. What is the physiological basis of the night vision loss?
- Special senses: tuning fork tests · ApplicationA 35-year-old woman has progressive conductive hearing loss in the left ear due to otosclerosis. What do tuning fork tests show?
- Special senses: vestibular function · ApplicationIn a healthy person, cold water is irrigated into the right external ear canal during caloric testing. What nystagmus is expected?
- Special senses: olfaction · ApplicationAfter a road traffic accident with fracture of the cribriform plate, a young man cannot smell coffee but can sense the pungency of ammonia. Which structures were most l…
- Special senses: macular sparing · Multi-stepA man has an acute right homonymous hemianopia after an occipital stroke, but central vision is preserved. Which explanation is most accurate?
- Special senses: relative afferent pupillary defect · Multi-stepA woman with left optic neuritis has a normal-looking pupil size. On the swinging flashlight test, what happens when the light moves from the right eye to the left eye?
- Special senses: tuning fork tests · ApplicationA 62-year-old man's Weber test lateralises to the right ear, and Rinne test shows air conduction better than bone conduction in both ears. What is the likely diagnosis?
- Special senses: vestibular caloric test · Multi-stepDuring caloric testing of a conscious healthy patient, cold water is irrigated into the right external ear. What eye movement follows?
- Special senses: colour vision · ApplicationA man with red-green colour blindness marries a woman with normal vision whose family has no colour blindness. What are the expected outcomes in their children?
- Special senses: pupillary light reflex pathway · Multi-stepAfter a head injury, a man's right pupil is 7 mm and does not constrict when light is shone into either eye. The left pupil is 3 mm and constricts normally to light in…
- Special senses: semicircular canals · Multi-stepA volunteer is rotated in a chair at constant speed with eyes closed for one minute and then stopped abruptly. She feels she is rotating in the opposite direction and s…
- Special senses: otolith organs · ApplicationA passenger in a lift feels heavier at the moment the lift starts moving upward. Which receptor organ mainly detects this vertical linear acceleration?
- Special senses: motion sickness · ApplicationA passenger reading in a ship's cabin becomes nauseated, sweaty and pale as the ship rolls, although the eyes see a still room. Which mechanism best explains the sympto…
- Special senses: magnocellular visual pathway · Multi-stepA lesion selectively damages the magnocellular layers of the lateral geniculate nucleus on both sides. Which visual function is most affected?
- Special senses: amblyopia · Multi-stepA 9-year-old child has a dense unilateral congenital cataract present since birth, removed only now. Despite a clear lens and a good prescription, vision in that eye st…
- Special senses: cortical visual areas · Multi-stepAfter a stroke involving the lateral occipitotemporal cortex, a man sees shapes normally but can no longer perceive colours, seeing the world in shades of grey. Which c…
Cardiovascular16
- Cardiovascular: haemodynamics · ApplicationA vasodilator drug doubles the radius of a systemic arteriole while the pressure gradient across it and the blood viscosity stay constant. By what factor does flow thro…
- Cardiovascular: arterial compliance · ApplicationA 72-year-old woman has a blood pressure of 170/70 mmHg with a normal stroke volume. Which change in the arterial system best explains her wide pulse pressure?
- Cardiovascular: coronary circulation · ApplicationA 55-year-old man with coronary artery disease develops angina when his heart rate rises from 70 to 150 per minute during exercise. Which mechanism most directly reduce…
- Cardiovascular: cerebral circulation · ApplicationAn anxious 22-year-old hyperventilates and complains of lightheadedness and tingling around the mouth. Which change in the cerebral circulation contributes to the light…
- Cardiovascular: pulmonary circulation · Multi-stepA lowlander living at 4500 m develops raised pulmonary artery pressure. Which statement explains why alveolar hypoxia has this effect on the lung but not on the systemi…
- Cardiovascular: pulse pressure in aortic regurgitation · ApplicationA 28-year-old man with severe aortic regurgitation has a blood pressure of 160/45 mmHg. Which mechanism best explains the very wide pulse pressure?
- Cardiovascular: mitral stenosis opening snap · Multi-stepIn two patients with rheumatic mitral stenosis, the interval from the aortic component of the second sound (A2) to the opening snap is 0.06 s in one and 0.12 s in the o…
- Cardiovascular: bedside manoeuvres in hypertrophic cardiomyopathy · ApplicationA 22-year-old athlete has a systolic ejection murmur from dynamic left ventricular outflow obstruction. Which manoeuvre would reduce the intensity of the murmur?
- Cardiovascular: coronary steal · Multi-stepDuring a dipyridamole stress perfusion scan, a patient with a 90% stenosis of one coronary artery develops chest pain and a reversible perfusion defect in that territor…
- Cardiovascular: heart sounds in atrial septal defect · Multi-stepA 20-year-old woman has a wide second heart sound whose splitting does not vary with breathing. Which explanation fits an atrial septal defect?
- Cardiovascular: Fick principle · Multi-stepIn a resting patient, oxygen consumption is 300 mL/min, arterial oxygen content is 19 mL/dL, pulmonary artery oxygen content is 14 mL/dL and heart rate is 75 per minute…
- Cardiovascular: turbulent flow and anaemia · ApplicationA 25-year-old woman with a haemoglobin of 5 g/dL has a soft systolic murmur over the precordium and no structural heart disease. Which change in the Reynolds number exp…
- Cardiovascular: Bezold-Jarisch reflex · ApplicationThirty minutes after an inferior wall myocardial infarction, a man has heart rate 42 per minute, blood pressure 80/50 mmHg, warm skin and clear lungs. Which reflex best…
- Cardiovascular: haemodynamics of hypovolaemic shock · Multi-stepA man with a ruptured spleen has a heart rate of 120 per minute, blood pressure 95/80 mmHg, cold clammy extremities and an estimated 25% blood loss. Which haemodynamic…
- Cardiovascular: Korotkoff sounds · ApplicationWhile measuring blood pressure with a cuff, the examiner hears tapping sounds that begin when cuff pressure falls to 120 mmHg and disappear when it falls to 80 mmHg. Wh…
- Cardiovascular: ECG in pre-excitation · ApplicationA 19-year-old with palpitations has an ECG showing a PR interval of 0.09 s with a slurred upstroke at the start of a broad QRS complex. Which mechanism explains the sho…
Endocrine14
- Endocrine: appetite regulation · ApplicationA 3-year-old child has severe obesity with relentless hunger since infancy and an undetectable serum leptin level. Replacement of which hormone is most likely to correc…
- Endocrine: ectopic ACTH and dexamethasone suppression · Multi-stepA 55-year-old smoker with small cell lung cancer has hypokalaemia, high plasma ACTH and high cortisol. Cortisol does not fall after high-dose dexamethasone (8 mg). What…
- Endocrine: familial hypocalciuric hypercalcaemia · Multi-stepA 30-year-old woman has asymptomatic mild hypercalcaemia with normal PTH, and her father has the same. Her 24-hour urinary calcium is low, with a calcium-to-creatinine…
- Endocrine: thyroid hormone binding · ApplicationA woman at 10 weeks of gestation has total T4 above the normal range, but normal TSH and free T4, and no symptoms. What is the explanation?
- Endocrine: pituitary stalk section · ApplicationAfter a road traffic accident, a man's pituitary stalk is transected. Which hormone level will rise?
- Endocrine: adrenal steroid synthesis · Multi-stepA girl born with virilised genitalia is found in early childhood to have hypertension and hypokalaemia, with raised 11-deoxycortisol and low renin. What causes the hype…
- Endocrine: aldosterone escape · Multi-stepA man with an aldosterone-secreting adenoma has hypertension and hypokalaemia but no peripheral oedema. What explains the absence of oedema?
- Endocrine: adrenal cortex zones · ApplicationA man with a pituitary macroadenoma has fatigue, hypoglycaemia and low blood pressure. His serum cortisol is low, but his potassium and plasma aldosterone are normal. W…
- Endocrine · ApplicationWhich gland releases insulin?
- Endocrine · ApplicationWhich hormone lowers serum calcium?
- Endocrine · ApplicationWhich hormone stimulates milk production?
- Endocrine · ApplicationWhich hormone raises blood glucose?
- Endocrine · ApplicationWhich hormone lowers blood glucose?
- Endocrine · ApplicationWhich gland releases cortisol?
Blood13
- Blood: haemostasis · Multi-stepA patient with a prolonged bleeding time, normal platelet count and normal PT has a prolonged aPTT that corrects after mixing with normal plasma. Which protein function…
- Blood: iron homeostasis · Multi-stepA 55-year-old woman with long-standing rheumatoid arthritis has haemoglobin 9.2 g/dL, MCV 78 fL, low serum iron, low total iron-binding capacity and serum ferritin 420…
- Blood: reticulocyte correction · ApplicationA patient has a haematocrit of 20% and a reticulocyte count of 6%. Taking the normal haematocrit as 45%, what is the corrected reticulocyte percentage (before any matur…
- Blood: Bombay phenotype · Multi-stepA woman's red cells show no agglutination with anti-A, anti-B or anti-H lectin, and her serum agglutinates group A, B and O red cells. She needs a transfusion. Which bl…
- Blood: warfarin and protein C · Multi-stepOn day 4 of warfarin started without heparin cover, a patient develops painful, well-demarcated skin necrosis over the thighs. What is the underlying mechanism?
- Blood: fibrinolysis · ApplicationA 28-year-old woman with heavy menstrual bleeding is given tranexamic acid. Through which mechanism does it reduce bleeding?
- Blood: haemoglobin variants · ApplicationA 24-year-old woman has haemoglobin 10.4 g/dL, MCV 62 fL, red cell count 5.8 million per microlitre and a normal serum ferritin. Her mother has similar findings. High-p…
- Blood: fetal haemoglobin · ApplicationA newborn's umbilical venous blood shows a higher oxygen affinity than maternal blood, even though both are exposed to the same 2,3-bisphosphoglycerate concentration. W…
- Blood: methaemoglobinaemia · Multi-stepA 30-year-old man on dapsone for dermatitis herpetiformis is cyanosed with pulse oximetry reading 85% that does not improve with oxygen. His arterial PaO2 is normal and…
- Blood: haem synthesis · ApplicationA 45-year-old man on isoniazid for tuberculosis develops microcytic hypochromic anaemia with ring sideroblasts. Impairment of which haem synthesis step is responsible?
- Blood · ApplicationWhich cells produce antibodies?
- Blood · ApplicationWhat protein carries O2 in RBC?
- Blood · ApplicationWhat cells form platelet plug?
Blood physiology12
- Blood physiology · ApplicationWhich protein carries most oxygen in blood?
- Blood physiology · ApplicationWhat is the main function of platelets?
- Blood physiology · ApplicationWhat protein forms the structural mesh of a blood clot?
- Blood physiology · ApplicationWhat cell lineage gives rise to platelets?
- Blood physiology · ApplicationWhat is the major function of albumin in plasma?
- Blood physiology · ApplicationWhat initiates the intrinsic coagulation pathway in laboratory testing?
- Blood physiology · ApplicationWhat protein carries most oxygen in blood?
- Blood physiology · ApplicationWhat is the principal role of erythrocytes?
- Blood physiology · ApplicationWhat is the main stimulus for erythropoietin secretion?
- Blood physiology · ApplicationWhich event initiates primary haemostasis after a vessel injury?
- Blood physiology · ApplicationWhat does the Bohr effect describe?
- Blood physiology · ApplicationWhich plasma protein is the major determinant of oncotic pressure?
Reproductive physiology12
- Reproductive physiology · ApplicationWhich hormone triggers ovulation in a normal cycle?
- Reproductive physiology · ApplicationWhat hormone prepares the endometrium for implantation after ovulation?
- Reproductive physiology · ApplicationWhat hormone stimulates follicular growth in the ovary?
- Reproductive physiology · ApplicationWhat hormonal event triggers ovulation?
- Reproductive physiology · ApplicationWhat is the principal action of prolactin after childbirth?
- Reproductive physiology · ApplicationWhat triggers ovulation in a normal menstrual cycle?
- Reproductive physiology · ApplicationWhat maintains the corpus luteum during early pregnancy?
- Reproductive physiology: menstrual cycle · ApplicationThe mid-cycle LH surge is triggered when sustained high estradiol exerts what feedback on the hypothalamic-pituitary axis?
- Reproductive physiology: lactation · ApplicationSuckling causes milk ejection by increasing release of which hormone from the posterior pituitary?
- Reproductive physiology · ApplicationWhich hormone causes milk ejection during breastfeeding?
- Reproductive physiology: ovulation · ApplicationWhich hormonal event directly triggers ovulation in a normal menstrual cycle?
- Reproductive physiology: lactation · ApplicationWhich hormone mediates milk ejection in response to infant suckling?
Nerve physiology11
- Nerve physiology: resting potential · Multi-stepA 55-year-old man with advanced kidney disease has a serum potassium of 7.8 mmol/L and generalised muscle weakness. Which change in his excitable membranes best explain…
- Nerve physiology: fibre susceptibility · ApplicationAfter a long period of pressure on the upper arm during deep sleep, a man wakes with wrist drop and loss of position sense in the hand, but pain sensation is relatively…
- Nerve physiology: regeneration · Multi-stepA 30-year-old woman has a clean transection of the ulnar nerve at the elbow, repaired surgically within hours. The first intrinsic hand muscle to be reinnervated lies a…
- Nerve physiology: cable properties · ApplicationTwo unmyelinated axons have the same membrane properties, but axon X has a larger diameter than axon Y. Which statement about passive spread of depolarisation is correct?
- Nerve physiology: toxins and channels · ApplicationA 35-year-old man develops perioral numbness, vomiting and progressive paralysis within an hour of eating pufferfish. He remains conscious. Which molecular action is re…
- Nerve physiology: calcium and excitability · ApplicationA 40-year-old woman develops perioral tingling and carpopedal spasm the day after total thyroidectomy. Her serum calcium is 1.6 mmol/L. Why has her nerve excitability i…
- Nerve physiology: compound action potential · Multi-stepA mammalian mixed nerve is stimulated supramaximally. The compound action potential recorded 10 cm from the stimulating electrode is lower and broader than the one reco…
- Nerve physiology: accommodation · Multi-stepIn a nerve preparation, a stimulating current is increased extremely slowly. The membrane is depolarised beyond the usual threshold potential, yet no action potential i…
- Nerve physiology: axonal transport · ApplicationA farmer bitten by a rabid dog on the hand later develops rabies encephalitis. By which process does the virus travel from the wound to the central nervous system?
- Nerve physiology · ApplicationWhich event causes the rapid depolarization phase of a neuronal action potential?
- Nerve physiology · ApplicationWhy does myelination increase nerve conduction velocity?
Cardiac physiology10
- Cardiac physiology · ApplicationWhich ionic movement produces the plateau (phase 2) of the ventricular myocyte action potential?
- Cardiac physiology: Frank-Starling · ApplicationAn intravenous fluid bolus increases the end-diastolic volume of the ventricle in a healthy person. Which change follows, by the Frank-Starling mechanism?
- Cardiac physiology: heart sounds · ApplicationA 68-year-old man with long-standing hypertension and left ventricular hypertrophy has a presystolic gallop heard just before the first heart sound. What produces this…
- Cardiac physiology: splitting of S2 · Multi-stepA 65-year-old man with complete left bundle branch block has a second heart sound whose split is widest during expiration and narrows on inspiration. What explains this…
- Cardiac physiology: pacemaker potential · ApplicationWhich ionic current contributes importantly to spontaneous phase-4 depolarisation in sinoatrial nodal cells?
- Cardiac physiology: Frank-Starling law · ApplicationAn increase in venous return raises stroke volume in an isolated healthy heart without changing contractility. Which principle explains this?
- Cardiac physiology: pressure-volume loop · Multi-stepWhich change shifts the end-systolic pressure-volume relation upward and leftward?
- Cardiac physiology: cardiac output · ApplicationCardiac output is calculated by multiplying which two variables?
- Cardiac physiology: Frank-Starling mechanism · ApplicationWhat is the Frank-Starling mechanism?
- Cardiac physiology: pressure-volume loop · ApplicationWhich change shifts the end-systolic pressure-volume relationship upward and leftward?
Acid-base physiology9
- Acid-base physiology · ApplicationWhat is the major extracellular buffer system?
- Acid-base physiology · ApplicationHow does the lung compensate for metabolic acidosis?
- Acid-base physiology · ApplicationWhat acid-base disorder follows sustained vomiting of gastric acid?
- Acid-base physiology · ApplicationWhat is the renal compensation for chronic respiratory acidosis?
- Acid-base physiology · ApplicationWhich primary disturbance is present in acute hypoventilation from opioid overdose?
- Acid-base physiology · ApplicationWhat is the expected respiratory compensation for metabolic acidosis?
- Acid-base physiology: respiratory compensation · Multi-stepA patient has metabolic acidosis from diabetic ketoacidosis. Which respiratory response is expected?
- Acid-base physiology · ApplicationWhat primary disorder has high pH and low arterial carbon dioxide?
- Acid-base physiology · ApplicationA patient has pH 7.28, bicarbonate 14 mmol/L, and low PaCO2 from hyperventilation. What primary acid-base disorder is present?
Acid-base8
- Acid-base: anion gap · Multi-stepA 24-year-old with type 1 diabetes has vomiting and deep, rapid breathing. Arterial pH is 7.18 and bicarbonate is 8 mmol/L. Serum sodium is 138, and chloride 96 mmol/L.…
- Acid-base: Henderson-Hasselbalch · Multi-stepAn arterial sample shows bicarbonate 12 mmol/L and PCO2 40 mmHg. Using pH = 6.1 + log [HCO3-] / (0.03 x PCO2), what is the pH?
- Acid-base: compensation and mixed disorders · Multi-stepA patient has pH 7.08, bicarbonate 10 mmol/L and PCO2 35 mmHg. Using Winter formula (expected PCO2 = 1.5 x HCO3 + 8, plus or minus 2), how should this be interpreted?
- Acid-base: normal anion gap acidosis · Multi-stepA 6-year-old with 2 days of watery diarrhoea has serum Na 138, K 3.0, Cl 112 and HCO3 14 mmol/L. What is the anion gap, and what is the likely cause of his acidosis?
- Acid-base: renal tubular acidosis · ApplicationA 7-year-old has failure to thrive, hypokalaemia, hyperchloraemic metabolic acidosis, urine pH 6.5 despite systemic acidosis, and nephrocalcinosis. Which defect is most…
- Acid-base: urinary anion gap · Multi-stepAfter 5 days of watery diarrhoea, a man has pH 7.28, serum bicarbonate 14 mmol/L, Na 138, Cl 114 and K 3.0 mmol/L. Urine Na 40, K 30 and Cl 80 mmol/L. What does the uri…
- Acid-base: compensation · Multi-stepAn exhausted patient with severe diarrhoea has pH 7.10, bicarbonate 12 mmol/L and PaCO2 40 mmHg. Which interpretation is correct?
- Acid-base: chronic respiratory acidosis · Multi-stepA patient with COPD has had stable hypercapnia with PaCO2 70 mmHg for several weeks. Which serum bicarbonate indicates appropriate renal compensation?
Immunity8
- Immunity: placental transfer of antibody · ApplicationA Rh-negative mother who did not receive anti-D prophylaxis after her first Rh-positive baby has a second Rh-positive fetus with hydrops. Which antibody class mediates…
- Immunity: complement · ApplicationA 20-year-old man has had two episodes of meningococcal meningitis. A total haemolytic complement (CH50) assay is near zero. Which defect is most likely?
- Immunity: immunoglobulin class switching · Multi-stepA 3-year-old boy has recurrent pyogenic sinopulmonary infections and Pneumocystis pneumonia. Serum IgM is high, while IgG, IgA and IgE are very low. Which molecule is m…
- Immunity: delayed hypersensitivity · ApplicationA tuberculin skin test is read at 48 to 72 hours rather than within minutes. What is the basis of this time course?
- Immunity: class switching · ApplicationA 2-year-old boy has recurrent sinopulmonary infections and Pneumocystis pneumonia. Serum IgM is elevated, IgG and IgA are very low, and B-cell numbers are normal. Whic…
- Immunity: leukocyte adhesion deficiency · ApplicationA 3-month-old infant had delayed umbilical cord separation and now has recurrent skin infections without pus formation. Blood neutrophil count is very high. Which neutr…
- Immunity: antigen processing · ApplicationA child has a mutation of the transporter associated with antigen processing (TAP), with low MHC class I surface expression and recurrent respiratory infections. Which…
- Immunity · ApplicationWhat is first line innate barrier?
Exercise physiology7
- Exercise physiology · ApplicationDuring sustained dynamic aerobic exercise such as running, which change occurs in the cardiovascular system?
- Exercise physiology · ApplicationDuring moderate exercise, what happens to cardiac output?
- Exercise physiology · ApplicationWhat happens to cardiac output during moderate exercise?
- Exercise physiology · ApplicationWhat limits maximal oxygen uptake during intense whole-body exercise in healthy adults?
- Exercise physiology: oxygen consumption · ApplicationAt maximal exercise, which variable most directly limits further rise in oxygen consumption in a healthy young adult?
- Exercise physiology · ApplicationWhy does skeletal-muscle blood flow rise during exercise?
- Exercise physiology · ApplicationWhat is the major immediate source of ATP during the first few seconds of maximal skeletal-muscle contraction?
Membrane transport7
- Membrane transport · ApplicationWhat transport mechanism moves sodium out of cells using ATP?
- Membrane transport · ApplicationWater moves across a semipermeable membrane mainly by what process?
- Membrane transport · ApplicationWhat transport mechanism moves glucose into many cells down its gradient through a carrier?
- Membrane transport · ApplicationWhat process uses ATP directly to move ions against a gradient?
- Membrane transport · ApplicationWhat pump moves sodium out of cells using ATP?
- Membrane transport · ApplicationWhat process moves water across a semipermeable membrane?
- Membrane transport · ApplicationWhat is the role of the sodium-potassium ATPase?
Renal and acid-base7
- Renal and acid-base: metabolic alkalosis · Multi-stepA 5-week-old infant with projectile vomiting has plasma Cl 82 mmol/L, K 2.9 mmol/L and bicarbonate 38 mmol/L, yet the urine is acidic. What explains the paradoxical aci…
- Renal and acid-base: proximal renal tubular acidosis · Multi-stepA 4-year-old child with Fanconi syndrome has glycosuria with normal blood glucose, phosphaturia, aminoaciduria and a hyperchloraemic metabolic acidosis with serum bicar…
- Renal and acid-base: osmolal gap · Multi-stepA man brought in with blurred vision and confusion after drinking an unknown liquid has a high anion gap metabolic acidosis. Measured serum osmolality is 330 mOsm/kg, w…
- Renal and acid-base: titratable acid · ApplicationWhen urine is titrated back to the pH of plasma (7.4) with alkali, the amount of alkali needed is the titratable acidity. Which urinary buffer accounts for most of it?
- Renal and acid-base: Henderson-Hasselbalch ratio · ApplicationIn a healthy person, plasma pH is 7.4, bicarbonate is 24 mmol/L and PCO2 is 40 mmHg. Given that dissolved CO2 is 0.03 x PCO2, what is the ratio of bicarbonate to dissol…
- Renal and acid-base: glucose threshold and splay · ApplicationDuring an infusion of glucose, glucose appears in urine when plasma glucose is about 200 mg/dL, although the average transport maximum has not yet been reached. What ex…
- Renal and acid-base: cystatin C as a GFR marker · ApplicationIn a patient with cachexia and very low muscle mass, serum creatinine gives a falsely reassuring estimate of renal function. Which endogenous marker, freely filtered an…
Respiration7
- Respiration · ApplicationWhich of the following shifts the oxygen–haemoglobin dissociation curve to the right?
- Respiration · ApplicationThe central chemoreceptors in the medulla respond mainly to a change in which of the following?
- Respiration · ApplicationWhat is the main stimulus for ventilation in healthy adults?
- Respiration · ApplicationWhich value is increased in dead-space ventilation?
- Respiration · ApplicationWhat muscle is main for quiet inspiration?
- Respiration · ApplicationWhat does hemoglobin mainly carry?
- Respiration · ApplicationWhat shifts O2 curve right?
GI6
- GI · ApplicationWhat stimulates gastric acid secretion?
- GI · ApplicationWhat is the main function of bile salts?
- GI · ApplicationWhat enzyme begins starch digestion in mouth?
- GI · ApplicationWhat initiates protein digestion in stomach?
- GI · ApplicationWhat pancreatic enzyme digests fat?
- GI · ApplicationWhat absorbs most nutrients?
Sleep physiology6
- Sleep physiology · ApplicationWhich sleep stage is associated with vivid dreaming and rapid eye movements?
- Sleep physiology · ApplicationWhat sleep stage is associated with slow-wave sleep?
- Sleep physiology · ApplicationWhich stage is associated with vivid dreaming and rapid eye movements?
- Sleep physiology · ApplicationWhich sleep stage is most associated with vivid dreaming and skeletal-muscle atonia?
- Sleep physiology · ApplicationWhich sleep stage is associated with vivid dreaming and skeletal-muscle atonia?
- Sleep physiology · ApplicationWhich sleep stage is associated with vivid dreaming, skeletal-muscle atonia, and variable autonomic activity?
Thermoregulation6
- Thermoregulation · ApplicationA 4-year-old with a bacterial infection has a temperature of 39 degrees C. At the onset she shivered and had cold hands. What is the basic mechanism of her fever?
- Thermoregulation · ApplicationWhat response promotes heat loss?
- Thermoregulation · ApplicationWhat response is initiated when core temperature rises?
- Thermoregulation · ApplicationWhat response occurs when core temperature rises?
- Thermoregulation · ApplicationWhich response is expected when core body temperature rises above its hypothalamic set point?
- Thermoregulation · ApplicationWhich response is most important for heat conservation in a cold environment?
Endocrine pancreas5
- Endocrine pancreas: insulin secretion · ApplicationWhich sequence describes how a rise in blood glucose triggers insulin secretion from the pancreatic beta cell?
- Endocrine pancreas: glucagon · Multi-stepA malnourished alcoholic patient with severe hypoglycaemia does not respond to intramuscular glucagon. What is the most likely reason?
- Endocrine pancreas: C-peptide · Multi-stepA 33-year-old woman has recurrent unexplained hypoglycaemic episodes. During an episode her plasma glucose is 38 mg/dL with high insulin, low C-peptide and a negative s…
- Endocrine pancreas: C-peptide · ApplicationA nurse has recurrent fasting hypoglycaemia with high serum insulin, low C-peptide and negative sulfonylurea screen. What is the cause?
- Endocrine pancreas: glucagon signalling · ApplicationA 55-year-old woman with a pancreatic alpha cell tumour has hyperglycaemia and weight loss. Which second messenger pathway mediates the action of the excess hormone on…
Adrenal4
- Adrenal: aldosterone excess · Multi-stepA 45-year-old man has blood pressure 168/102 mmHg, serum potassium 2.9 mmol/L, a raised aldosterone and a low plasma renin. Which acid-base disturbance is expected?
- Adrenal: ACTH and pigmentation · ApplicationA 38-year-old woman with tuberculous adrenalitis has hypotension, hyponatraemia and hyperpigmentation of the palmar creases and buccal mucosa. Why does skin pigmentatio…
- Adrenal: dexamethasone suppression · Multi-stepA 34-year-old woman with Cushingoid features has raised ACTH. Her cortisol does not suppress with 1 mg low-dose dexamethasone but falls by more than 50% with high-dose…
- Adrenal: steroid biosynthesis · Multi-stepA 10-day-old boy has vomiting, weight loss, serum sodium 123 mmol/L, potassium 6.4 mmol/L and hyperpigmented genitalia. Deficiency of 21-hydroxylase is suspected. Which…
Cardiovascular reflexes4
- Cardiovascular reflexes · ApplicationDuring carotid sinus massage a 60-year-old man's heart rate and blood pressure fall. Which nerve carries the afferent signal from the carotid sinus to the brainstem?
- Cardiovascular reflexes: Valsalva · Multi-stepA healthy volunteer performs a Valsalva manoeuvre. At the moment of release (phase IV), what happens to blood pressure and heart rate, and why?
- Cardiovascular reflexes: Cushing reflex · Multi-stepA 30-year-old man with a head injury and rising intracranial pressure has blood pressure 190/100 mmHg, heart rate 48 per minute and irregular breathing. What is the mos…
- Cardiovascular reflexes: Bainbridge reflex · ApplicationA rapid intravenous saline infusion raises right atrial pressure in a healthy volunteer, and the heart rate increases even though arterial pressure is unchanged. Which…
Membrane physiology4
- Membrane physiology · ApplicationWhat is the main determinant of resting membrane potential in many cells?
- Membrane physiology: action potentials · ApplicationThe rapid upstroke of a typical neuronal action potential is caused mainly by what?
- Membrane physiology: resting potential · ApplicationWhich ion has the greatest influence on the resting membrane potential of a typical neuron?
- Membrane physiology: action potential · ApplicationWhat causes the rapid depolarization phase of a neuronal action potential?
Neuromuscular junction4
- Neuromuscular junction · ApplicationA patient given tubocurarine during surgery shows muscle paralysis. At the neuromuscular junction, what is the primary effect?
- Neuromuscular junction: myasthenia gravis · Multi-stepA 26-year-old woman has ptosis and diplopia that worsen towards the evening. Repetitive nerve stimulation at 3 Hz shows a progressive fall in the compound muscle action…
- Neuromuscular junction: Lambert-Eaton syndrome · Multi-stepA 62-year-old heavy smoker has proximal leg weakness, dry mouth and absent knee jerks. Strength and reflexes improve briefly after a 10-second maximal voluntary contrac…
- Neuromuscular junction: botulism · ApplicationA 7-month-old infant fed honey has constipation, a weak cry, poor feeding and symmetrical descending flaccid weakness. What is the action of the responsible toxin?
Temperature regulation4
- Temperature regulation · ApplicationWhat brain region is the major thermostat for body temperature?
- Temperature regulation · ApplicationWhich response is most important for heat loss during exercise in a warm environment?
- Temperature regulation · ApplicationDuring fever caused by bacterial pyrogens, what produces the initial sensation of chills?
- Temperature regulation · ApplicationWhere is the central thermoregulatory set point located?
Calcium homeostasis3
- Calcium homeostasis: PTH and phosphate · ApplicationA 50-year-old woman has serum calcium 11.8 mg/dL, low serum phosphate and a raised PTH. Which renal action of PTH explains the low phosphate?
- Calcium homeostasis: vitamin D · ApplicationA 45-year-old man with chronic kidney disease has low serum calcium and a raised PTH. Which step in vitamin D activation is mainly impaired?
- Calcium homeostasis: ionised calcium · Multi-stepA 26-year-old woman who is hyperventilating has carpopedal spasm and perioral paraesthesia. Her total serum calcium is normal. What explains the tetany?
Cardiac cycle3
- Cardiac cycle · ApplicationDuring which phase of the cardiac cycle are all valves closed while ventricular pressure is rising?
- Cardiac cycle: third heart sound · ApplicationA 62-year-old man with orthopnoea and bibasal crepitations has a low-pitched sound heard at the apex shortly after the second heart sound. What produces this sound?
- Cardiac cycle · ApplicationWhich phase includes isovolumetric contraction?
Cardiac electrophysiology3
- Cardiac electrophysiology: hyperkalaemia · Multi-stepA patient with acute kidney injury has serum potassium 7.2 mmol/L, and the ECG shows tall, narrow, peaked T waves. Which change in the ventricular action potential best…
- Cardiac electrophysiology: vagal effect on SA node · ApplicationA trained 24-year-old athlete has a resting heart rate of 46 per minute from high vagal tone. How does acetylcholine slow the sinoatrial node?
- Cardiac electrophysiology: AV nodal delay · ApplicationCarotid sinus massage in a patient with supraventricular tachycardia prolongs the PR interval and may terminate the rhythm. What is the cellular mechanism of the slowed…
Haemostasis3
- Haemostasis: antithrombin and heparin · Multi-stepA man with extensive deep vein thrombosis, whose father had recurrent venous thrombosis, shows almost no prolongation of aPTT despite escalating unfractionated heparin…
- Haemostasis: D-dimer · Multi-stepA patient with severe sepsis has platelets 40,000/uL, prolonged PT and aPTT, low fibrinogen and a markedly raised D-dimer. Why does D-dimer rise in this condition?
- Haemostasis · ApplicationWhat is the main role of platelets in primary haemostasis?
Sensory physiology3
Thyroid3
- Thyroid: peripheral conversion · ApplicationA 35-year-old woman in thyroid storm is given propylthiouracil rather than carbimazole. Besides inhibiting thyroid peroxidase, which additional action makes propylthiou…
- Thyroid: hormone transport · Multi-stepA 28-year-old woman on an oral contraceptive pill has a total thyroxine level above the reference range, with normal free thyroxine and normal TSH. She has no symptoms.…
- Thyroid: Graves disease · ApplicationA 32-year-old woman has weight loss, tremor, a diffuse goitre and exophthalmos. Her free T4 is raised and TSH is undetectable. Why does thyroid hormone production conti…
Anterior pituitary2
- Anterior pituitary: growth hormone axis · ApplicationA 6-year-old boy has severe short stature, with a raised growth hormone and a low IGF-1 level. He does not respond to growth hormone therapy. What is the most likely de…
- Anterior pituitary: prolactin regulation · ApplicationA 29-year-old woman on risperidone develops amenorrhoea and galactorrhoea with a raised serum prolactin and a normal pituitary scan. What is the mechanism?
Autonomic physiology2
Cardiac2
Cardiac mechanics2
- Cardiac mechanics: Laplace law · Multi-stepIn a patient with dilated cardiomyopathy, the left ventricular radius increases from 2 cm to 3 cm. If intracavitary pressure and wall thickness stay the same, what happ…
- Cardiac mechanics: pressure-volume loop · Multi-stepOn a left ventricular pressure-volume loop, a sudden rise in aortic pressure (increased afterload) is imposed with unchanged preload and contractility. Which change occ…
Cardiac output2
Cell2
Cell physiology2
ECG2
- ECG: electrical axis · ApplicationIn a 6-year-old with long-standing pulmonary stenosis, the ECG shows a predominantly negative QRS in lead I and a positive QRS in lead aVF. What does this indicate?
- ECG: electrical axis · ApplicationAn ECG shows a predominantly positive QRS in lead I and predominantly negative QRS in leads II and aVF, with an axis of about minus 50 degrees and a normal QRS duration…
Female reproductive physiology2
- Female reproductive physiology · ApplicationIn the middle of the menstrual cycle, which event triggers the preovulatory LH surge?
- Female reproductive physiology: pregnancy · ApplicationIn the first trimester of pregnancy, which hormone maintains the corpus luteum so that progesterone production continues?
Fetal circulation2
Gastrointestinal hormones2
- Gastrointestinal hormones · ApplicationAfter a fatty meal, a hormone released from duodenal I cells causes gallbladder contraction and relaxation of the sphincter of Oddi. Which hormone is it?
- Gastrointestinal hormones · Multi-stepA woman on long-term high-dose proton pump inhibitor therapy has a raised fasting serum gastrin level, with no gastrinoma. What is the best explanation?
Hearing2
Muscle2
Neurons2
Respiratory2
- Respiratory: surfactant and alveolar stability · Multi-stepWithout surfactant, two connected alveoli of different radii have the same surface tension. According to the Laplace relation, what happens, and how does surfactant help?
- Respiratory: 2,3-BPG and stored blood · ApplicationA patient receives massive transfusion of red cells stored for 3 weeks in a blood bank. How is oxygen delivery to tissues initially affected through the haemoglobin dis…
Spinal reflexes2
- Spinal reflexes: reciprocal inhibition · ApplicationWhen the patellar tendon is tapped, the quadriceps contracts and the hamstrings relax at the same time. Which mechanism produces the hamstring relaxation?
- Spinal reflexes: tetanus · ApplicationA farmer with a puncture wound of the foot develops trismus, risus sardonicus and painful generalised spasms triggered by noise. Which neural mechanism accounts for the…
Vision2
Blood pressure1
Cardiovascular endocrinology1
Coagulation1
Fluid balance1
Gastrointestinal system1
Male reproductive physiology1
Synaptic physiology1
Common questions
How many Physiology questions are there?
951 original questions across 740 topics, and the bank grows over time.
Which Physiology topics are covered?
Cardiac cycle, Renal physiology, Respiration, Cardiac physiology, Sensory physiology, Muscle physiology, Cardiovascular reflexes, Water balance: water deprivation test, Special senses: hearing, Thermoregulation, Female reproductive physiology, Cardiovascular physiology: blood pressure, and more.
How difficult are these Physiology questions?
0 are recall, 677 are application and 274 are multi-step. The tags are our own editorial judgement, not an official difficulty rating.
Are these Physiology questions from past papers?
No. They are original practice items. NBEMS does not publish its paper or an official key, and we do not use recalled or leaked questions.
Can I practise Physiology for free?
Yes. The free plan includes 20 practice questions a day across all subjects, and a full Physiology subject test. A paid term removes the daily limit.
Is there a timed Physiology test?
Yes. The Physiology subject test is included on the free plan, with a countdown and a question palette.
How should I use these Physiology questions?
Answer before you look, read the reason for every option, and write a three-line note for each mistake. A few questions you fully review are worth more than many you skim.
Have these Physiology questions been reviewed by faculty?
Not yet. They are original and drafted with AI assistance, then edited by our team. Independent faculty review is planned, and each item shows its status. Confirm important facts in a standard textbook.