Cardiovascular system: shift of cerebral autoregulation in hypertension: practice question

A Physiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Physiology · Cardiovascular system: shift of cerebral autoregulation in hypertension

Sample item

A 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 transient visual deficit. Which statement best explains this?

AIntracranial pressure rises sharply whenever systemic pressure fallsBFalling blood pressure raises cerebral PCO2 and shuts down flowCHis cerebral autoregulation curve is shifted to the right, so the lower limit now exceeds the new pressureDCerebral vessels in hypertension dilate fully and are unable to constrict

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. His cerebral autoregulation curve is shifted to the right, so the lower limit now exceeds the new pressure

Chronic hypertension thickens cerebral arterioles and moves the autoregulatory range to higher pressures. A pressure that would be normal for most people can therefore lie below the lower limit for this patient, so cerebral flow becomes pressure-dependent and falls. This is why severe hypertension is lowered gradually.

Option by option

A. Intracranial pressure rises sharply whenever systemic pressure falls
Intracranial pressure does not rise with a fall in systemic pressure; the problem is perfusion.
B. Falling blood pressure raises cerebral PCO2 and shuts down flow
Hypoperfusion would raise PCO2 and dilate vessels, so it does not shut flow down.
C. His cerebral autoregulation curve is shifted to the right, so the lower limit now exceeds the new pressure (correct)
Correct. The rightward shift raises the lower limit of autoregulation, so a normal pressure becomes hypoperfusion.
D. Cerebral vessels in hypertension dilate fully and are unable to constrict
Chronic hypertension causes remodelled, thickened vessels, not fully dilated ones.

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.

Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is C, His cerebral autoregulation curve is shifted to the right, so the lower limit now exceeds the new pressure. Chronic hypertension thickens cerebral arterioles and moves the autoregulatory range to higher pressures.

Why is "Intracranial pressure rises sharply whenever systemic pressure falls" not the answer?

Intracranial pressure does not rise with a fall in systemic pressure; the problem is perfusion.

Why is "Falling blood pressure raises cerebral PCO2 and shuts down flow" not the answer?

Hypoperfusion would raise PCO2 and dilate vessels, so it does not shut flow down.

Why is "Cerebral vessels in hypertension dilate fully and are unable to const…" not the answer?

Chronic hypertension causes remodelled, thickened vessels, not fully dilated ones.

What concept does this question test?

It tests Cardiovascular system: shift of cerebral autoregulation in hypertension in Physiology. A pressure that would be normal for most people can therefore lie below the lower limit for this patient, so cerebral flow becomes pressure-dependent and falls. This is why severe hypertension is lowered gradually.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Cardiovascular system: shift of cerebral autoregulation in hypertension?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.