MODEL OF SEMI-CIRCULAR CANAL

t0

tslugthead

R

r

endolymph

-Slug of endolymph in a model of a horizontal SCC

-Forces acting on the slug are ???

VESTIBULAR SYSTEM

Its function is to control posture and eye movements.

Vestibules (and cochlea) are imbedded in the temporal bone of the skull and are surroundedby perilymph (similar to cerebrospinal fluid).

The vestibular apparatus consists of 3 orthogonal semi-circular canals as well as 2 bulbous enlargements called the utricle and saccule. The interior of the canals, utricle and saccule are filled with endolymph which is quite different, ionically, from perilymph (high K+ and low Na+ concentrations).

VESTIBULAR II

Semicircular Canals sense rotational acceleration

Clockwise movement of the head leads to counterclockwise deflection of hair cells resulting in depolarization of cells on the right side and hyperpolarization of cells on the left side. Hair cells are oriented in specific directions.

Otolith Organs sense linear acceleration

The utricle and saccule detect linear acceleration. Hair cells are embedded in a gelatinous macula which has ‘otolithic stones (calcium carbonate) riding on top of of it within the endolymph. Otolithic hair cells are not oriented in any particular direction.