Main Model
Cranial Nerves : VIII Vestibulocochlear nerve
Vestibulocochlear Nerve (CN VIII)
Functions: Special sensory (special somatic afferent) - that is, specia sensations of hearing, equilibrium, and motion (acceleration/deceleration).
Nuclei: Vestibular nuclei are located at the junction of the pons and medulla in the lateral part of the floor of the 4th ventricle; the cochlear nuclei, anterior and posterior, are in the medulla.
The vestibulocochlear nerve (CN VIII) emerges from the junction of the pons and medulla and enters the internal acoustic meatus. Here it separates into the vestibular and cochlear nerves.
• The vestibular nerve is composed of the central processes of bipolar neurons in the vestibular ganglion. The peripheral processes of the neurons extend to the maculae of the utricle and saccule (sensitive to linear acceleration and the pull of gravity relative to the position of the head) and to the cristae of the ampullae of the semicircular ducts (sensitive to rotational acceleration).
• The cochlear nerve is composed of the central processes of bipolar neurons in the spiral ganglion; the peripheral processes of the neurons extend to the spiral organ for the sense of hearing.
Within the internal acoustic meatus, the two divisions of CN VIII are accompanied by the primary root and intermediate nerve of CN VII and the labyrinthine artery.