Figure 3. The glossopharyngeal-hypoglossal reflex. Electrical stimulation of the glossopharyngeal nerve innervating the posterior tongue and pharynx induces polysynaptic reflexes in hypoglossal motoneurons. A similar effect occurs with stimulation of the superior laryngeal nerve that innervates the hypopharynx and larynx. The primary effect is excitation of motoneurons innervating the genioglossus and tongue intrinsic muscles.