Membrane physiology: action potentials: 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 · Membrane physiology: action potentials

Sample item

The rapid upstroke of a typical neuronal action potential is caused mainly by what?

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

The answer and the reasoning

D. Opening of voltage-gated sodium channels

Once threshold is reached, rapid sodium influx through voltage-gated sodium channels depolarises the neuronal membrane. Potassium efflux then repolarises it.

Option by option

  • A. Calcium pump activation

    Pumps maintain gradients over time but do not cause the fast upstroke.

  • B. Opening of voltage-gated potassium channels

    Potassium-channel opening primarily produces repolarisation.

  • C. Chloride influx through ligand-gated channels

    Chloride influx generally hyperpolarises neurons.

  • D. Opening of voltage-gated sodium channels (correct)

    Correct. Sodium conductance drives phase 0 in neurons.

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, Opening of voltage-gated sodium channels. Once threshold is reached, rapid sodium influx through voltage-gated sodium channels depolarises the neuronal membrane.

Why is "Calcium pump activation" not the answer?

Pumps maintain gradients over time but do not cause the fast upstroke.

Why is "Opening of voltage-gated potassium channels" not the answer?

Potassium-channel opening primarily produces repolarisation.

Why is "Chloride influx through ligand-gated channels" not the answer?

Chloride influx generally hyperpolarises neurons.

What concept does this question test?

It tests Membrane physiology: action potentials in Physiology. Potassium efflux then repolarises it.

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 Membrane physiology: action potentials?

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.