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

Which ion influx is primarily responsible for the rapid depolarization phase of a typical neuronal action potential?

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

The answer and the reasoning

D. Sodium

Opening of voltage-gated sodium channels causes rapid sodium influx and membrane depolarization in a typical neuron; subsequent potassium efflux contributes to repolarization and after-hyperpolarization.

Option by option

  • A. Chloride

    Chloride influx generally hyperpolarizes or stabilizes the membrane.

  • B. Potassium

    Potassium mainly exits during repolarization.

  • C. Calcium only

    Calcium is central in some cells but is not the main rapid upstroke in a typical neuron.

  • D. Sodium (correct)

    Correct: sodium entry drives the rapid upstroke of the neuronal action potential.

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, Sodium. Opening of voltage-gated sodium channels causes rapid sodium influx and membrane depolarization in a typical neuron; subsequent potassium efflux contributes to repolarization and after-hyperpolarization.

Why is "Chloride" not the answer?

Chloride influx generally hyperpolarizes or stabilizes the membrane.

Why is "Potassium" not the answer?

Potassium mainly exits during repolarization.

Why is "Calcium only" not the answer?

Calcium is central in some cells but is not the main rapid upstroke in a typical neuron.

What concept does this question test?

It tests Neurophysiology in Physiology. The correct option holds because: Correct: sodium entry drives the rapid upstroke of the neuronal action potential.

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.