Glossary of Hearing Terms
Central Auditory Pathway (Beyond the Inner Ear)
The “shearing motion,” stimulating the hair cells, causes impulses to be sent beyond the cochlea to the auditory (VIIIth) nerve. The auditory nerve carries the information to the brain via the brainstem for decoding. There are auditory centers in the brain that interpret the stimulus enabling the understanding of what is being heard. If these parts of the brain are badly damaged or are not stimulated for a long period of time, a person may not be able to hear speech (even at high levels) despite the fact that the auditory nerve has transmitted it to the brain.
The inner ear, the end organ of hearing, contains both the cochlea and the vestibular system that works to keep the body balanced (your equilibrium). The snail-shaped cochlea contains what are called “hair cells” that are not really hairs, but microscopic cells that connect to approximately 24,000 nerve fibers which are essential for hearing. The rocking of the stapes in the oval window moves fluid within the cochlea causing a “shearing” action or movement of the hair cells. This shearing action causes the hair cells to send an electrical impulse to the auditory nerve (VIIIth nerve).
The middle ear contains the three smallest bones in the body: the malleus, incus and stapes. These bones conduct sound through the air filled middle ear and transfer the sound to the inner ear. These bones are known as the “ossicles” and are connected to form the “ossicular chain.” The last bone in the chain is pushed in and out of the oval window of the cochlea. The eustachian tube, which equalizes pressure between the ear and the environment, is also found in the middle ear.
The outer ear consists of the external ear (pinna or auricle), the ear canal (external auditory meatus) and the ear drum (tympanic membrane). The outer ear directs sound into the ear canal and carries it to the eardrum. When these sound vibrations reach the eardrum, the eardrum begins to vibrate.
Tinnitus is a condition that may include roaring, buzzing, clicking, whistling, hissing, or high pitched ringing in the ears or inside the head. Tinnitus may be constant or occur intermittently in one or both ears and varies greatly among individuals ranging from a mild occasional sound to an ever present chronic condition.