Lab 10 - Cranial Nerve Nuclei and Brain Stem Circulation

Cranial Nerve IX - Glossopharyngeal Nerve

The components of the Glossopharyngeal Nerve include:

Cranial Nerve IX-Glossopharyngeal NerveThe inferior Salivatory nucleus is too small to be seen here, but is located superior to the solitary tract. The axons of the inferior salivatory nucleus travel in the glossopharyngeal (IX) nerve as parasympathetic efferents and synapse in the otic ganglion. The postganglionic axons of the otic ganglion innervate the parotid gland. Damage to the lower motor neurons results in the impairment of salivary production.

At this level of the medulla (pontomedullary junction) the ambiguus nucleus is difficult to see.

Lesions of the glossopharyngeal nerve would result in loss of the pharyngeal (gag) reflex because the glossopharyngeal nerve contains somatosensory afferents innervating the pharynx. Section of the nerve would interfere with the afferent limb of the reflex arc.

Lesions would also result in the loss of the carotid sinus reflex because the glossopharyngeal nerve carries viscerosensory afferents innervating the carotid body and sinus.

Sensory loss would also follow section of the glossopharyngeal nerve. Gustatory input from the posterior 1/3 of the tongue and pharynx as well as somatosensory input from the outer ear, tympanic membrane and middle ear would be affected.

Clinical Testing of Cranial Nerves IX and X: