In an angiogram of the head and neck, the carotid sinus is located at the bifurcation of the common carotid artery. Which nerve carries the afferent limb of the carotid sinus reflex (baroreceptor) to the brainstem?

• A Hering's nerve (a branch of the glossopharyngeal nerve, CN IX) ✓
• B Superior cervical sympathetic fibers
• C Vagus nerve (CN X) via the pharyngeal plexus
• D Internal branch of the superior laryngeal nerve

Explanation

Hering's nerve (carotid sinus nerve) is a branch of the glossopharyngeal nerve (CN IX) that carries baroreceptor afferents from the carotid sinus and chemoreceptor afferents from the carotid body to the nucleus tractus solitarius (NTS) in the medulla. The NTS then activates the dorsal motor nucleus of the vagus for the efferent parasympathetic response (bradycardia, vasodilation). The vagus contributes to the carotid body innervation via the superior cervical ganglion branch, but the primary afferent for the sinus reflex is Hering's nerve (CN IX branch).

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.