Final answer:
The afferent nerve for the gag reflex is the glossopharyngeal nerve, and the efferent nerve is the vagus nerve. They are responsible for the sensory input and motor response of the reflex, respectively.
Step-by-step explanation:
Gag Reflex Nerves
The afferent limb of the gag reflex is primarily mediated by the glossopharyngeal nerve (cranial nerve IX), which relays sensory information, including taste and general sensations from the pharyngeal walls, to the brain. This sensory input can trigger the gag reflex. For the efferent limb, the motor response which contracts the muscles of the pharynx is largely controlled by the vagus nerve (cranial nerve X). The facial nerve is not principally involved in the gag reflex but is related to taste and facial expressions. When testing the gag reflex, stimulation of the lateral wall of the fauces with a tongue depressor should lead to an equivalent response on both sides, indicating proper function of these nerves.
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