Neurophysiology and special senses: descending pain modulation: 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 and special senses: descending pain modulation

Sample item

Which brainstem nucleus releases serotonin in the descending pathway that activates enkephalin interneurons to inhibit dorsal horn pain transmission?

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

The answer and the reasoning

D. Nucleus raphe magnus

The periaqueductal grey activates the nucleus raphe magnus in the medulla, whose serotonergic fibres descend to the dorsal horn and excite enkephalin-releasing interneurons that inhibit pain transmission.

Option by option

  • A. Substantia nigra

    The substantia nigra is dopaminergic and part of the motor circuit.

  • B. Nucleus ambiguus

    The nucleus ambiguus supplies motor fibres to pharyngeal and laryngeal muscles.

  • C. Locus coeruleus

    The locus coeruleus uses noradrenaline rather than serotonin.

  • D. Nucleus raphe magnus (correct)

    Correct. Raphe magnus neurons release serotonin in the descending analgesic pathway.

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, Nucleus raphe magnus. The periaqueductal grey activates the nucleus raphe magnus in the medulla, whose serotonergic fibres descend to the dorsal horn and excite enkephalin-releasing interneurons that inhibit pain transmission.

Why is "Substantia nigra" not the answer?

The substantia nigra is dopaminergic and part of the motor circuit.

Why is "Nucleus ambiguus" not the answer?

The nucleus ambiguus supplies motor fibres to pharyngeal and laryngeal muscles.

Why is "Locus coeruleus" not the answer?

The locus coeruleus uses noradrenaline rather than serotonin.

What concept does this question test?

It tests Neurophysiology and special senses: descending pain modulation in Physiology. The correct option holds because: Correct. Raphe magnus neurons release serotonin in the descending analgesic pathway.

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 and special senses: descending pain modulation?

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.