Cardiovascular system: autonomic control of circulation: 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: autonomic control of circulation

Sample item

A 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 has failed?

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

The answer and the reasoning

B. Baroreflex-mediated sympathetic vasoconstriction and cardioacceleration

On standing, blood pools in the legs and the baroreflex normally raises heart rate and vasoconstricts through sympathetic outflow. In autonomic neuropathy this reflex fails, so pressure falls without tachycardia. Slower hormonal responses cannot correct the drop within seconds.

Option by option

  • A. The Frank-Starling mechanism of the ventricle

    Frank-Starling is intrinsic to the heart and is not damaged by autonomic neuropathy.

  • B. Baroreflex-mediated sympathetic vasoconstriction and cardioacceleration (correct)

    Correct. A fixed pulse with falling pressure means the sympathetic baroreflex limb has failed.

  • C. Renin release from the juxtaglomerular cells

    Renin acts over minutes to hours and does not explain the immediate failure.

  • D. Myogenic autoregulation of brain vessels

    Cerebral autoregulation is local and is not responsible for the absent heart rate rise.

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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Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is B, Baroreflex-mediated sympathetic vasoconstriction and cardioacceleration. On standing, blood pools in the legs and the baroreflex normally raises heart rate and vasoconstricts through sympathetic outflow.

Why is "The Frank-Starling mechanism of the ventricle" not the answer?

Frank-Starling is intrinsic to the heart and is not damaged by autonomic neuropathy.

Why is "Renin release from the juxtaglomerular cells" not the answer?

Renin acts over minutes to hours and does not explain the immediate failure.

Why is "Myogenic autoregulation of brain vessels" not the answer?

Cerebral autoregulation is local and is not responsible for the absent heart rate rise.

What concept does this question test?

It tests Cardiovascular system: autonomic control of circulation in Physiology. In autonomic neuropathy this reflex fails, so pressure falls without tachycardia. Slower hormonal responses cannot correct the drop within seconds.

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: autonomic control of circulation?

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.