Question

Choose the best answer(s) with respect to auditory fibers:

a)     Type I fibers innervate inner hair cells

b)     Type II fibers innervate outer hair cells

c)     Type I fibers innervate outer hair cells

d)     a & b

Answer 1

Auditory nerve fibers are the fibers that send signals from the hair cells of inner ear cochlea to the cochlear nucleus of the brainstem. The hair cells in the cochlea have afferent innervation via peripheral fibers of the spiral ganglionic neurons. They are of two types:

a. Type 1 nerve fibers: These larger radially myelinated unbranched fibers have one ending and are connected to the inner hair cells. These fibers connect the inner hair cells to the cochlear nuclei. Only a single fiber connects each hair cell. Hence, they receive more afferent output as well providing rapid discrete coding.

b. Type II nerve fibers: These are small unmyelinated ganglion fibers which are known to enter organ of Corti by spiraling basally. They connect to outer hair cells. One type II nerve fiber connects many outer hair cells as human ear has more outer hair cells than inner hair cells.

Right choice: d. both a & b.