The human inner ear contains two divisions, the hearing portion (cochlea) and the balance portion or vestibular system
The vestibular system consists of a network of tubes (the semi circular canals) and sacs
(utricle). Because
its structure is so complex, the inner ear is often referred to as the
vestibular labyrinth.
The labyrinth is filled with fluid that moves when the position of the head
changes; as this fluid moves, it bends tiny hairs of sensory cells inside the canals and sacs. Bending the hair initiates nerve impulses to the
brain; in response, the brain sends commands to your eyes to enable you to see clearly as you move and to your muscles allowing you to maintain your balance as you sit, stand and move about.
Vertigo, the sudden sensation that you are unsteady or that your surroundings are moving, usually results from a problem with the nerves and the structures of the balance mechanism in your inner ear (vestibular system), which sense movement and changes in your head position. Abnormal rhythmic eye movements (nystagmus) almost always accompany vertigo.
