Cardiovascular system: Poiseuille law: 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: Poiseuille law

Sample item

Atherosclerosis narrows a femoral artery to half its original radius, with all other factors constant. By what factor does resistance to flow rise?

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

The answer and the reasoning

A. 16 times

Poiseuille's law states resistance is inversely proportional to the fourth power of the radius. Halving radius raises resistance by 2 to the power 4, which is 16 times. Small radius changes therefore control flow in arterioles.

Option by option

  • A. 16 times (correct)

    Correct. Resistance varies as 1/r to the fourth power, so half the radius gives 16 times.

  • B. 4 times

    Four times would apply to a square relationship.

  • C. 8 times

    Eight times would apply to a cubic relationship.

  • D. 2 times

    Doubling would apply if resistance were inversely proportional to radius itself.

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, 16 times. Poiseuille's law states resistance is inversely proportional to the fourth power of the radius.

Why is "4 times" not the answer?

Four times would apply to a square relationship.

Why is "8 times" not the answer?

Eight times would apply to a cubic relationship.

Why is "2 times" not the answer?

Doubling would apply if resistance were inversely proportional to radius itself.

What concept does this question test?

It tests Cardiovascular system: Poiseuille law in Physiology. Halving radius raises resistance by 2 to the power 4, which is 16 times. Small radius changes therefore control flow in arterioles.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. 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: Poiseuille law?

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.