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 ion influx causes rapid neuronal depolarization?

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

The answer and the reasoning

A. Sodium influx

Opening voltage-gated sodium channels allows rapid sodium entry, producing the rising depolarization phase of a typical neuronal action potential.

Option by option

  • A. Sodium influx (correct)

    Correct: sodium influx produces the action-potential upstroke.

  • B. Calcium efflux

    Calcium efflux does not cause the usual neuronal upstroke.

  • C. Potassium influx

    Potassium efflux is more important in repolarization.

  • D. Chloride influx

    Chloride influx usually hyperpolarizes cells.

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, Sodium influx. Opening voltage-gated sodium channels allows rapid sodium entry, producing the rising depolarization phase of a typical neuronal action potential.

Why is "Calcium efflux" not the answer?

Calcium efflux does not cause the usual neuronal upstroke.

Why is "Potassium influx" not the answer?

Potassium efflux is more important in repolarization.

Why is "Chloride influx" not the answer?

Chloride influx usually hyperpolarizes cells.

What concept does this question test?

It tests Neurophysiology in Physiology. The correct option holds because: Correct: sodium influx produces the action-potential upstroke.

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.