Neurophysiology: referred 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: referred pain

Sample item

A 58-year-old man has retrosternal pain during exertion that radiates to the inner side of the left arm. Which mechanism best explains the radiation?

AVisceral afferents travelling in the vagus nerve to the armBDirect spread of the visceral pain impulse along the brachial plexusCConvergence of visceral and somatic afferents from the same spinal segments onto common dorsal horn neuronesDSensitisation of arm nociceptors by cardiac metabolites

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

The answer and the reasoning

C. Convergence of visceral and somatic afferents from the same spinal segments onto common dorsal horn neurones

Cardiac nociceptive afferents enter the cord at about T1 to T4 and converge on the same second-order neurones that receive somatic input from the medial arm. The brain, used to somatic input, projects the pain to the body surface of that dermatome, which is the convergence-projection theory. This explains referred pain in conditions such as angina.

Option by option

A. Visceral afferents travelling in the vagus nerve to the arm
Cardiac pain afferents travel with sympathetic nerves, not the vagus.
B. Direct spread of the visceral pain impulse along the brachial plexus
Impulses do not spread peripherally between organs and nerves; the convergence is in the spinal cord.
C. Convergence of visceral and somatic afferents from the same spinal segments onto common dorsal horn neurones (correct)
Correct. Shared second-order neurones cause misattribution.
D. Sensitisation of arm nociceptors by cardiac metabolites
Metabolites act on cardiac nociceptors and do not sensitise arm receptors.

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.

Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is C, Convergence of visceral and somatic afferents from the same spinal segments onto common dorsal horn neurones. Cardiac nociceptive afferents enter the cord at about T1 to T4 and converge on the same second-order neurones that receive somatic input from the medial arm.

Why is "Visceral afferents travelling in the vagus nerve to the arm" not the answer?

Cardiac pain afferents travel with sympathetic nerves, not the vagus.

Why is "Direct spread of the visceral pain impulse along the brachial plexus" not the answer?

Impulses do not spread peripherally between organs and nerves; the convergence is in the spinal cord.

Why is "Sensitisation of arm nociceptors by cardiac metabolites" not the answer?

Metabolites act on cardiac nociceptors and do not sensitise arm receptors.

What concept does this question test?

It tests Neurophysiology: referred pain in Physiology. The brain, used to somatic input, projects the pain to the body surface of that dermatome, which is the convergence-projection theory. This explains referred pain in conditions such as angina.

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: referred 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.