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Introduction to Meniere's Disease
The Human Ear and Meniere's Disease
The organs of the inner ear are responsible for two important functions:
- hearing
- balance
Hearing
When sound enters the ear canal, the sound waves cause the tympanic membrane to vibrate. This sets the ossicles into a vibratory motion. Since the bottom of the stapes touches the oval window, vibrations of the middle ear cause disturbances of the fluid in the inner ear. The movement of the perilymph disturbs the small hairs in the cochlea which then generate nerve impulses that travel to the brain via the auditory portion of the vestibulocochlear nerve. The impulse is translated by the brain into sound.
Balance
The organs of the vestibular system (semicircular canals and vestibule) also contain hair cells which, when disturbed by the moving endolymph, detect either rotation of the head, movement (acceleration and deceleration), or position in space. When a person moves or changes direction, the endolymph is disturbed and moves within the vestibule and the semicircular canals. The direction of movement determines which movement or position hair cells are stimulated. The hair cells then generate a nerve impulse which travels via the vestibulocochlear nerve to the brain stem, cerebellum, or spinal cord and we reflexively move in such a way to counter the direction of movement thus maintain our balance.
