Autonomic nervous system: nicotine action at ganglia: practice question

A Pharmacology 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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Pharmacology · Autonomic nervous system: nicotine action at ganglia

Sample item

In a toxicology lecture, nicotine is described as stimulating autonomic ganglia at low doses and blocking them at high doses. What is the basis of the block at high doses?

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

The answer and the reasoning

D. Persistent depolarisation of the receptor

Nicotine opens the ganglionic nicotinic channel, but at high concentration the membrane stays depolarised and cannot respond, giving a depolarising block. Succinylcholine blocks the motor end plate in a similar way.

Option by option

  • A. Blockade of choline uptake into the nerve terminal

    Blocking choline uptake is the action of hemicholinium, not nicotine.

  • B. Competitive block of muscarinic receptors

    Nicotine acts on nicotinic receptors and has no action as a muscarinic antagonist.

  • C. Inhibition of acetylcholine synthesis

    Nicotine does not interfere with acetylcholine synthesis.

  • D. Persistent depolarisation of the receptor (correct)

    Correct. Prolonged depolarisation makes the ganglion cell unresponsive.

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 Pharmacology question

What is the answer to this Pharmacology question?

The best answer is D, Persistent depolarisation of the receptor. Nicotine opens the ganglionic nicotinic channel, but at high concentration the membrane stays depolarised and cannot respond, giving a depolarising block.

Why is "Blockade of choline uptake into the nerve terminal" not the answer?

Blocking choline uptake is the action of hemicholinium, not nicotine.

Why is "Competitive block of muscarinic receptors" not the answer?

Nicotine acts on nicotinic receptors and has no action as a muscarinic antagonist.

Why is "Inhibition of acetylcholine synthesis" not the answer?

Nicotine does not interfere with acetylcholine synthesis.

What concept does this question test?

It tests Autonomic nervous system: nicotine action at ganglia in Pharmacology. Succinylcholine blocks the motor end plate in a similar way.

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 Autonomic nervous system: nicotine action at ganglia?

Learn drugs as classes, then the exception in each class that an examiner would pick. Then use the flashcards and the other Pharmacology 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.