Physiology of ear- innervation

 

The vestibulocochlear nerve has two divisions. 

  • The cochlear division has its receptors placed in the hair cells of the organ of Corti. The  first order neurons  have their cell bodies in a spiral line in the base of the bony spiral lamina of the organ. They are therefore referred to as spiral ganglia. These sound receptors in the organ of Corti are inner and outer hair cells, which are supported by other cells. Membrana tectoria lies over the cells. The inner hair cells form one layer of 4000 columnar cells, which lie against the inner rods. Each of the inner hair cells have about 100 acoustic small hair projection from its surface. The outer hair are more numerous, but similar to the inner hair. The central processes of the nerve fibers run in the cochlear nerve.

  • The vestibular division is more complex. It runs peripherally in five nerves. They are 

    • Lateral semicircular nerve

    • Posterior semicircular nerve

    • Superior semicircular nerve

    • Utricular nerve

    • Saccular nerve

Their receptors lie in the hair cells of the maculae of utricle and saccule for static balance and in the ampullae of semicircular ducts for kinetic balance. Their  cell bodies lie in the vestibular ganglia in the internal acoustic meatus. Their central processes then come to form the vestibular nerve that accompanies the cochlear nerve to the brainstem.

 

 

 

 

 

 

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