Gag Reflex Afferent — MFDS Part 1 MCQ

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EasyAnatomy (Head & Neck)Gag Reflex AfferentMFDS Part 1

During bedside testing, touching the posterior pharyngeal wall elicits the gag reflex. Which cranial nerve carries the sensory afferent limb of this reflex?

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Correct answer: D — Glossopharyngeal nerve (IX)

The glossopharyngeal nerve (cranial nerve IX) carries sensory information from the posterior pharyngeal wall and forms the afferent limb of the clinically tested gag reflex. The efferent response—elevation of the soft palate and contraction of the pharyngeal musculature—is mediated predominantly by the vagus nerve (X) through the pharyngeal plexus, making option B the principal distractor. The trigeminal nerve supplies much of the facial and oral somatic sensation but is not the standard afferent limb tested here. The facial nerve supplies muscles of facial expression, while the hypoglossal nerve provides motor innervation to the tongue.

Reference: University Hospitals Coventry and Warwickshire NHS Trust, Clinical Skills Workbook, section “Cranial Nerve 9 & 10 – Glossopharyngeal & Vagus,” 2022–2023. https://uhmeded.uhcw.nhs.uk/Portals/0/AssetUploads/CHESS%20Book%20Clinical%20Skills%20Workbook%202022-23.pdf?ver=ELcRsPPRSWHk3baBgJ2INQ%3D%3D