Auditory nerve which is also known as cochlear nerve is a nerve in the ear that carries nerve impulses to the brain. It is a sensory nerve that carries acoustic energy to the brain.
Auditory nerve starts from within the cochlea and goes up to the brainstem where the fibers of the auditory nerve make contact with the cochlear nucleus. The number of nerve fibers within the cochlear nerve average around 30,000.
Cochlea is located within the inner ear. The sound vibrations that reach the cochlea move the tiny hairs that are attached to the nerve fibers. The sounds get converted to signals and are sent to the brain via the auditory nerve. Disease, damage or deformity of the cochlear hair cells can cause hearing impairment or deafness. The hair cell damage can be due to causes such as acoustic trauma, ototoxic drugs, bacterial and viral infection, autoimmune disease and genetic disorders. The cells that are malfunctioning may send intermittent or unclear signals or they may not send any signals at all.
A hearing aid in such cases is of no use. A hearing aid can only amplify the sound. On the other hand cochlear implant is a bit more complex electronic device. The cochlear implant bypasses the external and the middle ears and stimulates the electrodes implanted in the cochlea to introduce the signals to be carried to the brain. A microphone located behind-the-ear hearing aid converts the sound waves into electrical signals that are carried by a thin wire to a sound processor worn on a belt or carried in a pocket. This processor converts electrical signals into digital signals.
The digital signals from the processor are carried via the same wire to a transmitter located on the head. The transmitter sends radio signals to a receiving unit embedded just under the scalp. The receiving unit stimulates the wire implanted in the cochlea to send clear signal to the auditory nerve. The presence of auditory nerve fibers is necessary for proper functioning of this device.
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