1. Cell bodies in superior olivary nucleus
2. Axons form efferent fibers of the C.N. VIII
3. Some axons terminate on the outer hair cells
a. outer hair cells are motor; can lengthen or shorten
b. length change alters the position of the tectorial membrane, thus changing the sensitivity of the inner hair cells
c. postulated functions
1) amplification to increase hearing sensitivity (replace some of the sound energy lost through viscous damping for low intensity sounds)
2) attenuation to protect inner hair cells from excess displacement (high intensity sounds)
3) sharpening of frequency discrimination (increase sensitivity at regions of maximum basilar membrane displacement, decrease sensitivity at adjacent areas)
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Note: When functioning as an acoustic amplifier, the outer hair cells generate sound wave that can be detected by a microphone placed in the ear; this forms the basis of the otoacoustic test often used in assessing hearing in newborns
4. Some axons terminate on sensory axon endings
a. axon-axonal synapses
b. postulated function: control hearing sensitivity
