Neck: carotid sinus reflex: practice question

A Anatomy 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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Anatomy · Neck: carotid sinus reflex

Sample item

A 68-year-old man faints when turning his head while wearing a tight collar. Pressure over the carotid sinus produces bradycardia and hypotension. Which nerves form the afferent and efferent limbs of the arc causing the bradycardia?

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

The answer and the reasoning

C. Afferent through the glossopharyngeal nerve; efferent through the vagus nerve

The carotid sinus, at the origin of the internal carotid artery, contains baroreceptors that signal through the sinus nerve (Hering) to the glossopharyngeal nerve and the nucleus of the tractus solitarius. Pressure mimics a rise in blood pressure and reflexly increases vagal tone to the sinoatrial node, causing bradycardia, with reduced sympathetic outflow causing vasodilatation. Carotid sinus hypersensitivity causes syncope in the elderly.

Option by option

  • A. Afferent through the glossopharyngeal nerve; efferent through the sympathetic chain

    Sympathetic outflow is inhibited, not activated, because the baroreflex lowers heart rate and pressure.

  • B. Afferent through the vagus nerve; efferent through the glossopharyngeal nerve

    The roles of the two nerves are reversed here; the vagus is the efferent limb.

  • C. Afferent through the glossopharyngeal nerve; efferent through the vagus nerve (correct)

    Correct. The glossopharyngeal nerve carries the afferent signals and the vagus carries the efferent bradycardic signals.

  • D. Afferent through the accessory nerve; efferent through the vagus nerve

    The accessory nerve is motor to two muscles and carries no baroreceptor afferents.

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 Anatomy question

What is the answer to this Anatomy question?

The best answer is C, Afferent through the glossopharyngeal nerve; efferent through the vagus nerve. The carotid sinus, at the origin of the internal carotid artery, contains baroreceptors that signal through the sinus nerve (Hering) to the glossopharyngeal nerve and the nucleus of the tractus solitarius.

Why is "Afferent through the glossopharyngeal nerve; efferent through the sym…" not the answer?

Sympathetic outflow is inhibited, not activated, because the baroreflex lowers heart rate and pressure.

Why is "Afferent through the vagus nerve; efferent through the glossopharynge…" not the answer?

The roles of the two nerves are reversed here; the vagus is the efferent limb.

Why is "Afferent through the accessory nerve; efferent through the vagus nerve" not the answer?

The accessory nerve is motor to two muscles and carries no baroreceptor afferents.

What concept does this question test?

It tests Neck: carotid sinus reflex in Anatomy. Pressure mimics a rise in blood pressure and reflexly increases vagal tone to the sinoatrial node, causing bradycardia, with reduced sympathetic outflow causing vasodilatation. Carotid sinus hypersensitivity causes syncope in the elderly.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 Neck: carotid sinus reflex?

Learn every nerve by its route, its muscles and what a lesion looks like at the bedside. That one habit answers a large share of questions. Then use the flashcards and the other Anatomy 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.