Nerve and muscle: strychnine: 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 · Nerve and muscle: strychnine

Sample item

A man develops violent generalised convulsions with preserved consciousness after ingesting a rodenticide. The poison acts at which site?

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

The answer and the reasoning

A. Spinal cord glycine receptors, which it blocks

Strychnine is a competitive antagonist of glycine receptors, mainly in the spinal cord and brainstem. Loss of glycinergic inhibition makes motor neurones hyperexcitable, producing exaggerated reflexes and extensor spasms triggered by minor stimuli while consciousness is preserved.

Option by option

  • A. Spinal cord glycine receptors, which it blocks (correct)

    Correct. Blocking glycine receptors removes spinal inhibition.

  • B. Neuromuscular junction nicotinic receptors, which it activates

    Activating nicotinic receptors would cause depolarisation block, not reflex spasms with preserved consciousness.

  • C. Motor nerve terminal calcium channels, which it opens

    Opening presynaptic calcium channels is not its mechanism.

  • D. Cortical GABA-A receptors, which it potentiates

    Potentiation of GABA-A receptors would sedate and not cause convulsions.

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.

More Physiology questions

Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is A, Spinal cord glycine receptors, which it blocks. Strychnine is a competitive antagonist of glycine receptors, mainly in the spinal cord and brainstem.

Why is "Neuromuscular junction nicotinic receptors, which it activates" not the answer?

Activating nicotinic receptors would cause depolarisation block, not reflex spasms with preserved consciousness.

Why is "Motor nerve terminal calcium channels, which it opens" not the answer?

Opening presynaptic calcium channels is not its mechanism.

Why is "Cortical GABA-A receptors, which it potentiates" not the answer?

Potentiation of GABA-A receptors would sedate and not cause convulsions.

What concept does this question test?

It tests Nerve and muscle: strychnine in Physiology. Loss of glycinergic inhibition makes motor neurones hyperexcitable, producing exaggerated reflexes and extensor spasms triggered by minor stimuli while consciousness is preserved.

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 Nerve and muscle: strychnine?

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.