Muscle physiology: 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 · Muscle physiology

Sample item

What causes rigor mortis after death?

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

The answer and the reasoning

D. ATP depletion prevents myosin detachment from actin

After death, ATP is depleted and calcium leaks from stores, allowing actin-myosin binding but preventing ATP-dependent detachment, producing stiffness.

Option by option

  • A. High oxygen delivery to muscle

    Oxygen delivery ceases after death.

  • B. Immediate collagen synthesis

    Collagen synthesis does not cause acute rigor.

  • C. Excess acetylcholine at neuromuscular junction

    Acetylcholine is not the primary postmortem cause.

  • D. ATP depletion prevents myosin detachment from actin (correct)

    Correct: ATP is required to detach cross-bridges.

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 D, ATP depletion prevents myosin detachment from actin. After death, ATP is depleted and calcium leaks from stores, allowing actin-myosin binding but preventing ATP-dependent detachment, producing stiffness.

Why is "High oxygen delivery to muscle" not the answer?

Oxygen delivery ceases after death.

Why is "Immediate collagen synthesis" not the answer?

Collagen synthesis does not cause acute rigor.

Why is "Excess acetylcholine at neuromuscular junction" not the answer?

Acetylcholine is not the primary postmortem cause.

What concept does this question test?

It tests Muscle physiology in Physiology. The correct option holds because: Correct: ATP is required to detach cross-bridges.

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 Muscle physiology?

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.