Neurophysiology: 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 · Neurophysiology

Sample item

What prevents an immediate second action potential in a neuron?

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

The answer and the reasoning

C. Sodium-channel inactivation

During the absolute refractory period, voltage-gated sodium channels are inactivated and cannot reopen until sufficient membrane repolarization has occurred.

Option by option

  • A. Chloride entry only

    Chloride entry alone is not the primary mechanism.

  • B. Calcium depletion

    Calcium depletion does not define the absolute refractory period.

  • C. Sodium-channel inactivation (correct)

    Correct: sodium-channel inactivation prevents immediate re-firing.

  • D. Potassium pump failure

    Pump failure is not the normal refractory-period mechanism.

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 C, Sodium-channel inactivation. During the absolute refractory period, voltage-gated sodium channels are inactivated and cannot reopen until sufficient membrane repolarization has occurred.

Why is "Chloride entry only" not the answer?

Chloride entry alone is not the primary mechanism.

Why is "Calcium depletion" not the answer?

Calcium depletion does not define the absolute refractory period.

Why is "Potassium pump failure" not the answer?

Pump failure is not the normal refractory-period mechanism.

What concept does this question test?

It tests Neurophysiology in Physiology. The correct option holds because: Correct: sodium-channel inactivation prevents immediate re-firing.

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 Neurophysiology?

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.