Synaptic 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 · Synaptic physiology

Sample item

Which event directly triggers neurotransmitter vesicle fusion at a chemical synapse?

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

The answer and the reasoning

B. Calcium influx into the presynaptic terminal

An action potential opens presynaptic voltage-gated calcium channels, and calcium entry triggers vesicle docking and fusion through SNARE-related mechanisms. Neurotransmitter then acts on postsynaptic receptors.

Option by option

  • A. Chloride removal from plasma

    Plasma chloride removal is not involved.

  • B. Calcium influx into the presynaptic terminal (correct)

    Correct. Presynaptic calcium is the immediate exocytosis trigger.

  • C. Sodium efflux from the postsynaptic cell

    Postsynaptic sodium movements occur after receptor activation.

  • D. Potassium influx into the cleft

    Potassium does not trigger vesicle fusion in this way.

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 into the presynaptic terminal. An action potential opens presynaptic voltage-gated calcium channels, and calcium entry triggers vesicle docking and fusion through SNARE-related mechanisms.

Why is "Chloride removal from plasma" not the answer?

Plasma chloride removal is not involved.

Why is "Sodium efflux from the postsynaptic cell" not the answer?

Postsynaptic sodium movements occur after receptor activation.

Why is "Potassium influx into the cleft" not the answer?

Potassium does not trigger vesicle fusion in this way.

What concept does this question test?

It tests Synaptic physiology in Physiology. Neurotransmitter then acts on postsynaptic receptors.

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 Synaptic 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.