Auditory system Flashcards
how many newborns have a hearing disorder?
4-6 out of 1000 (most common congenital illness)
why is hearing loss irreversible?
there is no regeneration of hair cells once they die
what % of adults have hearing impairment?
40% of adults over 75
what are the 2 universal newborn hearing screening?
- otoacoustic emissions
- auditory brainstem response
what is otoacoustic emissions test?
you put a speaker in babie’s ear and pick up the sounds that come out of the hair cells
what is auditory brainstem response test?
a more detailed test with electrodes on the forehead and on the auditory brainstem behind the ear
why is auditory brainstem response test better than otoacoustic? 2 reasons
- babies often have fluid in their ear, making the otoacoustic test unreliable
- auditory brainstem responses tells you that the whole auditory pathway is functional
what do vestibular hair cells respond to?
linear acceleration
what part of the ear is fluid filled
inner ear only
what frequencies activate cochlear vs vestibular hair cells?
vestibular hair cells are more sensitive to lower frequenceis
what is in the middle ear?
ossicles, between tympanic membrane and middle ear
what is the pitch of a sound?
the frequency of the sound
what level are audible frequencies?
20-20 000 Hz
what is the loudness of a sound? what can we hear?
the amplitude of the wave.
range 0.002 to 2000 dynes/cm^2
frequency response is determined by what?
the functional anatomy of the ear
what frequencies are human voices? (we are most sensitive to these frequencies)
500-5 000 Hz
what do decibels represent?
Weber-Fechners Law: decibels represent sound intensity in a way that corresponds to perceived loudness
what is Weber-Fechners Law formula?
L (loudness) = 20 x log10 (P/Pstd)
where P/Pstd = pressure / minimum pressure
where does auditory mechano-electrical transduction happen?
inner ear
what is the external auditory meatus?
auditory canal in external ear
what is the meatus function?
resonate the sound waves to ensure reliable transmission of speech (frequencies aren’t amplified, they just loose less energy)
what does the eustachian tube connect?
the middle ear to the pharynx
blocked eustachian tube can lead to what?
otitis media (middle ear infection from build up of fluid that slows down the ossicles)
is the eustachian tube normally open or closed?
normally closed; it opens during yawning to equilibrate pressure