Cardiac physiology: 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 · Cardiac physiology

Sample item

Which ionic movement produces the plateau (phase 2) of the ventricular myocyte action potential?

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

The answer and the reasoning

B. Calcium influx through L-type channels

Phase 0 is rapid sodium influx. Phase 2, the plateau, is maintained by inward calcium current through L-type channels balanced by outward potassium current. The long plateau prevents tetany and gives the ventricle time to empty.

Option by option

  • A. Sodium influx through fast channels

    Fast sodium channels cause the upstroke (phase 0) and then inactivate.

  • B. Calcium influx through L-type channels (correct)

    Correct. Calcium entry holds the membrane near zero and also triggers calcium-induced calcium release.

  • C. Potassium efflux through delayed rectifier channels

    Potassium efflux drives repolarisation in phase 3; during the plateau it merely balances the calcium current.

  • D. Chloride influx

    Chloride movement is not what shapes the ventricular 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 B, Calcium influx through L-type channels. Phase 0 is rapid sodium influx.

Why is "Sodium influx through fast channels" not the answer?

Fast sodium channels cause the upstroke (phase 0) and then inactivate.

Why is "Potassium efflux through delayed rectifier channels" not the answer?

Potassium efflux drives repolarisation in phase 3; during the plateau it merely balances the calcium current.

Why is "Chloride influx" not the answer?

Chloride movement is not what shapes the ventricular action potential.

What concept does this question test?

It tests Cardiac physiology in Physiology. Phase 2, the plateau, is maintained by inward calcium current through L-type channels balanced by outward potassium current. The long plateau prevents tetany and gives the ventricle time to empty.

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 Cardiac physiology?

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.