Neurophysiology: inhibitory synapse: 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: inhibitory synapse

Sample item

A patient with an acute seizure receives intravenous lorazepam. How does the drug enhance inhibitory synaptic transmission?

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

The answer and the reasoning

D. Increases the frequency of GABA-A chloride channel opening

Benzodiazepines bind a site on the GABA-A receptor and increase the frequency of channel opening in the presence of GABA. More chloride enters the neuron, which hyperpolarises it and reduces firing. Barbiturates instead prolong the duration of opening.

Option by option

  • A. Blocks voltage-gated sodium channels directly

    Direct sodium channel blockade is the action of phenytoin and carbamazepine.

  • B. Increases the duration of GABA-A channel opening

    Prolonged opening duration is the action of barbiturates.

  • C. Blocks NMDA receptors

    NMDA blockade is the action of ketamine and memantine.

  • D. Increases the frequency of GABA-A chloride channel opening (correct)

    Correct. Benzodiazepines increase how often the chloride channel opens when GABA is bound.

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, Increases the frequency of GABA-A chloride channel opening. Benzodiazepines bind a site on the GABA-A receptor and increase the frequency of channel opening in the presence of GABA.

Why is "Blocks voltage-gated sodium channels directly" not the answer?

Direct sodium channel blockade is the action of phenytoin and carbamazepine.

Why is "Increases the duration of GABA-A channel opening" not the answer?

Prolonged opening duration is the action of barbiturates.

Why is "Blocks NMDA receptors" not the answer?

NMDA blockade is the action of ketamine and memantine.

What concept does this question test?

It tests Neurophysiology: inhibitory synapse in Physiology. More chloride enters the neuron, which hyperpolarises it and reduces firing. Barbiturates instead prolong the duration of opening.

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: inhibitory synapse?

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.