The cochlear nerve, also known as the acoustic or auditory nerve, transfers auditory information from the inner ear to the brain. The cochlear nerve connects to the cochlea, which is one of the parts of the inner ear responsible for hearing.
When sound hits the ear drum, the vibrations are converted into an electrical signal which is then transmitted to the brain by the cochlear nerve. Humans have approximately 30,000 nerve fibers in the cochlear nerve, but animals more reliant on hearing, such as the domestic cat, have at least 50,000 nerve endings. The hair cells located on the cochlea are linked through the auditory nerve to the cochlear nucleus, which is located in the brain stem. Collectively, the cochlea and auditory nerves are called the spiral ganglion because of its shape. The cochlear organ is sensitive to many diseases and disorders. These disorders can damage the cochlea and the auditory nerve, which ultimately can result in partial to complete loss of hearing. Hearing loss can be mitigated by hearing aids or the installation of a cochlear implant. A cochlear implant is a surgically implanted device that produces a sense of sound for someone who has sustained damage to the hair cells on the cochlea. While these implants can restore or improve hearing, they are less effective than normal hearing, since less sound information is received by the brain.