Reflex elicited by touching the posterior wall of the pharynx. Pharyngeal muscles contract symmetrically elevating the soft palate. Actual gagging may or may not occur. Afferent loop involves the glossopharyngeal nerve, the efferent loop involves the vagus nerve.
a good example of a true reflex. It is "triggered" whenever a noxious substance touches the back of the tongue, back of the pharynx, or soft palate. The swallow response, on the other hand, cannot be initiated by touching any particular area in the oral cavity. The gag reflex and the swallow response also differ in terms of neurological control. The gag reflex is completely controlled by the brain stem. The swallow, on the other hand, is only partially controlled by the brain stem. It also receives cortical input, and input from muscle spindles, including feedback from tongue movements. (It is important to note that the gag reflex and the swallow response are not related. In the past, many physicians would determine feeding status based on the presence or absence of a patient's gag. Actually, the presence or absence of a gag reflex does not predict the status of the swallow response.)