Lab 10 - Cranial Nerve Nuclei and Brain Stem Circulation

Cranial Nerve IX - Glossopharyngeal Nerve

This section is at the level of the pontomedullary junction. This is the rostral limit of the ambiguus nucleus (axons exit brain in Cranial Nerves XI, X and IX). The spinal trigeminal nucleus and tract - (somatosensory afferents of Cranial Nerve V, VII, IX, X) are located anterior to the inferior vestibular nuclei and the solitary nucleus and tract. The solitary nucleus (chemosensory afferents of Cranial Nerve X, IX and VII) is reduced in size and at this rostral level and cannot be seen very clearly. It contains second order neurons of the gustatory system.

You should be able to locate the cochlear nuclear complex (cochlear afferents in Cranial Nerve VIII) which is labeled the dorsal and ventral cochlear nuclei. The medial and inferior vestibular nuclei (vestibular afferents in Cranial Nerve VIII) continue to be located in the superior portion of the tegmentum.

Blood Supply

Branches of the anterior spinal artery continue to supply the medial areas of the medulla that include the pyramids, medial lemniscus, and the medial region of the inferior olivary nucleus. Branches of the vertebral artery also continue to supply more lateral areas of the medulla, which include the lateral part of the inferior olivary nucleus and the reticular formation, which surrounds the nucleus ambiguus. At this level of the brain stem, branches of the anterior inferior cerebellar artery (AICA) are beginning to replace those of the posterior inferior cerebellar artery (PICA) to supply the posterolateral areas of the brain stem. The branches of the PICA and AICA supply the medial and inferior vestibular nuclei, the inferior and middle cerebellar peduncles, the dorsal and ventral cochlear nuclei, the solitary tract and nucleus, lateral parts of the reticular formation, the spinal trigeminal nucleus and tract, spinothalamic tracts, rubrospinal tract, medullary reticulospinal tract.