Chapter 8 - The Vestibular System

Abstract

The vestibular system of the inner ear is designed to detect linear acceleration (maculae) and angular acceleration (cristae). Both organs contain hair cells with stereocilia (“hairs”) that detect deflection toward or away from a polarizing kinocilium. Hair cells respond to these deflections by an increase or decrease in transmitter release, respectively, from a constant baseline release. This transmitter generates action potentials in the vestibular nerve fibers that are transmitted to the vestibular complex in the dorsolateral brain stem and to the vestibulocerebellum. The vestibular complex projects to: the spinal cord to change muscle tone in response to vestibular stimuli; the extraocular nuclei to stabilize the eyes with head movement (vestibulo-ocular reflex); the reticular formation to produce autonomic changes in response to vestibular stimulation; the thalamus for relay to the cortex for perception of movement; and interconnects with the vestibulocerebellum to allow for adjustment of vestibular responses due to changing conditions.