inner ear

or labyrinth of the ear

Part of the ear containing organs of hearing and equilibrium. The bony labyrinth has three sections (semicircular canals, vestibule, and cochlea); within each structure is a corresponding part of the membranous labyrinth (semicircular ducts, two saclike structures in the vestibule, and cochlear duct). Sound vibrations are transmitted from the middle ear through the membrane-covered oval window to fluid in the snail-shell-shaped cochlea, whose motion stimulates hair cells in the cochlea. The hair cells trigger nerve impulses that travel to the brain, which interprets them as sound. The vestibule and semicircular canals also have organs with hair cells. Those in the vestibule indicate the head's position with respect to the rest of the body (see proprioception). The three semicircular canals, at right angles to each other, signal motion of the head in three-dimensional space. Continued stimulation after motion stops causes a mismatch with visual input, experienced as dizziness or motion sickness.

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Organ of hearing and balance. The outer ear directs sound vibrations through the auditory canal to the eardrum, which is stretched across the end of the auditory canal and which transmits sound vibrations to the middle ear. There a chain of three tiny bones conducts the vibrations to the inner ear. Fluid inside the cochlea of the inner ear stimulates sensory hairs; these in turn initiate the nerve impulses that travel along the auditory nerve to the brain. The inner ear is also an organ of balance: the sensation of dizziness that is felt after spinning is caused when fluid inside the inner ear's semicircular canals continues to move and stimulate sensory hairs after the body has come to rest. The eustachian tube connects the middle ear with the nasal passages; that connection allows the common cold to spread from the nasal passages to the middle ear, especially in infants and small children. The most common cause of hearing loss is otosclerosis, a surgically correctable disease in which one of the bones of the middle ear loses its capacity to vibrate. Seealso deafness, otitis.

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Auditory means of or relating to the process of hearing:

• Auditory system, the neurological structures and pathways of sound perception.
• Sound, the physical signal perceived by the auditory system.
• Hearing (sense), is the auditory sense, the sense by which sound is perceived.
• Ear, the auditory end organ.
• Cochlea, the auditory branch of the inner ear.
• Auditory illusion, sound trick analogous to an optical illusion.
• Primary auditory cortex, the part of the higher-level of the brain that serves hearing.
• External auditory meatus, the ear canal
• Auditory scene analysis, the process by which a scene containing many sounds is perceived
• Auditory phonetics, the science of the sounds of language
• Auditory imagery, hearing in head in the absence of sound