Tuesday, June 26, 2018

Nuclei of Afferent Cranial Nerves

The nuclei of the cranial nerves afferent fibers are located in the brainstem (midbrain, pons, medulla oblongata). The vagus nerve afferent axons originate from the neurons in the jugular ganglion and ganglion nodosum (ganglion of the trunk), whereas the glossopharyngeal afferent axons emerge from the nerve cells in its ganglion superius and ganglion petrosum. The root fascicles of both nerves goes into the medulla oblongata along its dorsolateral groove, and the axons then bifurcate into ascending and descending rami, similar to those of the dorsal roots of the spinal nerves.

The ascending rami end in the nucleus alae cinereae nucleus vagi et glossopharyngeal); the descending rami come together to form a compact bundle called the tractus solitarius or trineural fasciculus, and terminating in a gray cell column called the nucleus of the solitary tract, which is a caudal prolongation of the nucleus alae cinereae. Both tract and nucleus become attenuated caudal, to disappear in the fourth cervical segment.

Down below, a sideview of the nuclei of cranial nerves sensory fibers