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Physiology · Cardiovascular: Bezold-Jarisch reflex
Sample itemThirty 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 explains the picture?
Original practice item, not a recalled exam question. Nothing here is recorded.
The answer and the reasoning
B. Bezold-Jarisch reflex, with vagal afferents from ventricular receptors causing bradycardia and vasodilatation
Ischaemic or chemically stimulated inferoposterior ventricular receptors send vagal C-fibre afferents to the medulla, which raises vagal tone and withdraws sympathetic tone, producing bradycardia, vasodilatation and hypotension. It is common in inferior infarction, after reperfusion and during spinal anaesthesia, and responds to atropine and fluids.
Option by option
A. Cushing reflex, with raised intracranial pressure and sympathetic surge
The Cushing reflex produces hypertension with bradycardia in raised intracranial pressure.
B. Bezold-Jarisch reflex, with vagal afferents from ventricular receptors causing bradycardia and vasodilatation (correct)
Correct. The triad of bradycardia, hypotension and warm skin is typical of this vagal reflex.
C. Bainbridge reflex, with atrial stretch causing tachycardia
The Bainbridge reflex increases heart rate when the atria are stretched.
D. Chemoreceptor reflex, with carotid body stimulation causing hypertension
Chemoreceptor stimulation raises sympathetic outflow and blood pressure.
Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.
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