Which cranial nerves are responsible for the gag reflex?

• A. Vagus (X) and Accessory (XI)
• B. Glossopharyngeal (IX) and Vagus (X)
• C. IX and X
• D. Trigeminal (V) and Facial (VII)

Answer: (C)

The gag reflex is a two-nerve reflex: sensory input travels through the glossopharyngeal nerve (IX) from the oropharynx, and the motor response is carried out by the vagus nerve (X). When the posterior tongue or oropharyngeal wall is stimulated, IX carries that sensation to the brainstem, where the signal is processed and sent via X to the pharyngeal muscles, causing contraction and a gag. This makes IX and X the correct pairing. The other nerves do not mediate this reflex—XI is mainly motor to neck muscles, while V and VII are involved in sensation/mastication and facial expression, not the gag response. If the gag reflex is absent, it points to dysfunction in IX, X, or their brainstem pathways.