About Hearing
In the normally functioning auditory
system, the outer and middle ears act as a bridge to transfer
acoustic pressure changes (sound waves) to the fluids of the
part of the inner ear known as the cochlea. This is accomplished
by one of the three small middle-ear bones pushing into and out
of the cochlea at a place called the oval window. The cochlea
is filled with liquid that carries the vibrations to thousands
of tiny hair cells sitting on a membrane that stretches the length
of the cochlea. The hair cells on the membrane fire off tiny
electrical signals. These electrical signals travel up the cochlea
nerves of the auditory pathway to the brain. All this happens
in a fraction of a second.
When the hair cells of the cochlea
are damaged or missing, the result is sensory hearing loss. However,
in most cases, when the sensory cells are damaged there is also
some loss of individual nerve fibres. Therefore, this type of
hearing impairment is typically called sensorineural, referring
to damage to both the sensory end organ and the nerve itself. |
|
