Chapters 19 & 20

auditory system consists of the:

outer ear, middle ear, inner ear, auditory nervous system

outer ear

collects and resonates sound, assists in localizing the direction of sounds, and helps protect the middle ear from damage

tympanic membrane/ear drum

separates the ear canal from the middle ear and transmits sound vibrations into the middle ear

middle ear

contains the ossicular chain (malleus, incus, stapes) which amplify the sound before reaching the inner ear

eustachian tubes

equalizes pressure in the ear, shorter and more horizontal in children

inner ear

consists of the cochlea and vestibule

cochlea

contains two fluid filled tubes and approximately 15,000 tiny hair cells which are stimulated by the cochlear fluid and send a neural impulse to the auditory nerve

auditory nervous system

sends neural (electrical) impulses from the cochlea to the auditory complex in the temporal lobes of the brain

central auditory nervous system

pathways and synapses in the brain responsible for sensation, auditory attention, auditory discrimination, auditory association, and auditory memory

Heschl’s gyrus

receives auditory signals from the ears and processes the signals as environmental sounds, human speech sounds, and human nonspeech sounds (coughs, burps)

conductive hearing loss

damage to the outer and/or middle ear (sound may be too weak to reach the cochlea)

otitis media

ear infection is the most common cause of hearing loss

pressure equalizing tubes (PE tubes)

a small silicone tube inserted into the tympanic membrane to equalize the air pressure between the middle ear cavity and the atmosphere

prenatal causes of hearing loss of the inner ear

development of the external, middle, and inner ear takes place between the 4th-8th week of gestation

perinatal causes

occur during the process of birth. sensorineural hearing loss occurs in 2-4% of neonatal intensive care unit survivors

ototoxic

drugs that have harmful effects on the central auditory nervous system