Neurophysiology and special senses: gate control of pain: 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: gate control of pain

Sample item

A child rubs the skin over a bumped knee and the pain eases. Which mechanism best explains this relief?

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

The answer and the reasoning

B. Large touch afferents excite inhibitory interneurons of the substantia gelatinosa, closing the pain gate

In the gate control theory, large myelinated touch fibres activate inhibitory interneurons in the substantia gelatinosa, which dampen transmission from nociceptive fibres to second-order neurons. Rubbing therefore reduces perceived pain.

Option by option

  • A. Rubbing releases endorphins that block transduction in nociceptors

    Endorphins act within the central nervous system and do not block transduction in the nociceptor endings.

  • B. Large touch afferents excite inhibitory interneurons of the substantia gelatinosa, closing the pain gate (correct)

    Correct. Touch afferents activate inhibitory interneurons that reduce pain transmission in the dorsal horn.

  • C. Touch afferents release substance P that depletes nociceptive transmitter

    Substance P is the transmitter of nociceptive fibres and touch fibres do not release it to deplete it.

  • D. Pressure causes conduction block in C fibres at the skin

    Rubbing does not selectively block C fibre conduction at the skin.

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, Large touch afferents excite inhibitory interneurons of the substantia gelatinosa, closing the pain gate. In the gate control theory, large myelinated touch fibres activate inhibitory interneurons in the substantia gelatinosa, which dampen transmission from nociceptive fibres to second-order neurons.

Why is "Rubbing releases endorphins that block transduction in nociceptors" not the answer?

Endorphins act within the central nervous system and do not block transduction in the nociceptor endings.

Why is "Touch afferents release substance P that depletes nociceptive transmi…" not the answer?

Substance P is the transmitter of nociceptive fibres and touch fibres do not release it to deplete it.

Why is "Pressure causes conduction block in C fibres at the skin" not the answer?

Rubbing does not selectively block C fibre conduction at the skin.

What concept does this question test?

It tests Neurophysiology and special senses: gate control of pain in Physiology. Rubbing therefore reduces perceived pain.

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: gate control of pain?

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.