Nerve and muscle: temperature and nerve conduction: 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.

Try it

Physiology · Nerve and muscle: temperature and nerve conduction

Sample item

A technician warms a cold limb before nerve conduction studies. Why does cooling falsely suggest a neuropathy?

ACooling raises the resting potential, so threshold is not reachedBCooling blocks all A fibres at onceCCooling slows channel gating, which reduces conduction velocityDCooling increases myelin thickness, so conduction slows

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

The answer and the reasoning

C. Cooling slows channel gating, which reduces conduction velocity

Sodium and potassium channel gating are temperature dependent. In a cold limb the action potential is prolonged and conduction velocity falls by a few metres per second per degree, which can mimic a demyelinating neuropathy. Studies are therefore done at a standard skin temperature.

Option by option

A. Cooling raises the resting potential, so threshold is not reached
Cooling does not make the resting potential less negative in a way that blocks conduction.
B. Cooling blocks all A fibres at once
Cooling does not block all A fibres at the temperatures reached in the limb.
C. Cooling slows channel gating, which reduces conduction velocity (correct)
Correct. Slowed channel kinetics lowers conduction velocity in the cold.
D. Cooling increases myelin thickness, so conduction slows
Cooling does not thicken myelin.

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, Cooling slows channel gating, which reduces conduction velocity. Sodium and potassium channel gating are temperature dependent.

Why is "Cooling raises the resting potential, so threshold is not reached" not the answer?

Cooling does not make the resting potential less negative in a way that blocks conduction.

Why is "Cooling blocks all A fibres at once" not the answer?

Cooling does not block all A fibres at the temperatures reached in the limb.

Why is "Cooling increases myelin thickness, so conduction slows" not the answer?

Cooling does not thicken myelin.

What concept does this question test?

It tests Nerve and muscle: temperature and nerve conduction in Physiology. In a cold limb the action potential is prolonged and conduction velocity falls by a few metres per second per degree, which can mimic a demyelinating neuropathy. Studies are therefore done at a standard skin temperature.

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 Nerve and muscle: temperature and nerve conduction?

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.