General physiology: gain of a feedback system: 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 · General physiology: gain of a feedback system

Sample item

In 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 only 25 mmHg. What is the gain of the baroreceptor feedback system?

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

The answer and the reasoning

A. -2

Gain equals the correction achieved divided by the error that remains. The reflex lowers the rise from 75 to 25 mmHg, a correction of 50 mmHg in the opposite direction, leaving an error of 25 mmHg. Gain = -50/25 = -2; the negative sign denotes negative feedback.

Option by option

  • A. -2 (correct)

    Correct. Correction (-50) divided by residual error (25) gives -2.

  • B. -0.5

    This inverts the ratio, dividing the residual error by the correction.

  • C. +2

    A positive gain would indicate positive feedback, which would amplify, not reduce, the disturbance.

  • D. -3

    This divides the uncontrolled disturbance by the residual error (75/25) instead of dividing the correction by the residual error.

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 A, -2. Gain equals the correction achieved divided by the error that remains.

Why is "-0.5" not the answer?

This inverts the ratio, dividing the residual error by the correction.

Why is "+2" not the answer?

A positive gain would indicate positive feedback, which would amplify, not reduce, the disturbance.

Why is "-3" not the answer?

This divides the uncontrolled disturbance by the residual error (75/25) instead of dividing the correction by the residual error.

What concept does this question test?

It tests General physiology: gain of a feedback system in Physiology. The reflex lowers the rise from 75 to 25 mmHg, a correction of 50 mmHg in the opposite direction, leaving an error of 25 mmHg. Gain = -50/25 = -2; the negative sign denotes negative feedback.

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 General physiology: gain of a feedback system?

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.