Ch 10.2: Ears & Hearing Flashcards
Frequency is measured in ___ while intensity and loudness are measured in ___
Hz; db
Human range of frequency
20-20,000Hz
Optimal range for loudness in humans
0-80db
Path of sound in outer ear
funneled by pinna —> external acoustic meatus —> tympanic membrane (eardrum)
Middle ear
air-filled cavity between tympanic membrane and the cochlea
Path of sound in middle ear
eardrum —> malleus —> incus —> stapes —> oval window —> cochlea
What does the stapedius muscle do?
dampens the stapes if sound is too intense
Chambers of the cochlea
1) upper chamber (scala vestibuli, portion of upper labyrinth)
2) lower bony chamber (scala tympani)
3) portion of scala media (cochlear duct)
4) helicotrema (small canal between scala vestibuli and scala tympani)
What fills cochlear chambers?
perilymph
What fills the cochlear duct?
endolymph
After reaching the oval window, vibrations displace _____ in ______
perilymph; scala vestibuli
Where are low frequency sounds received in the cochlea?
toward the apex
Sensory hair cells are located in the _____ projecting into _______ of the cochlear duct
basilar membrane, endolymph
Inner hair cells
3500 form one row the entire length of the basilar membrane
Inner hair cells are innervated by
10-20 sensory neurons of cranial nerve VIII that relay sound
Outer hair cells
11,500 in rows with 3 rows per turn
Outer hair cells are innervated by ________ that make them shorten when _________ and lengthen when ____________
depolarized; hyperpolarized
Hairs in the organ of corti are made of ____ that are large _____ arranged in _____
stereocilia; microvilli; bundles
Stereocilia are interconnected and ___ in size with each bundle
increase stepwise
Where do stereocilia embed in the organ of corti?
in a gelatinous tectorial membrane
Components of spiral organ
basilar membrane, inner hair cells, sensory fibers, tectorial membrane
Vibration of tectorial membrane bends stereocilia, results in the opening of _____ into the ________
K+ channels; endolymph
the ____ the amount of basilar membrane displaced/bending of stereocilia, the more _____ is released, producing a ____ receptor potential
greater; glutamate; greater
In place theory, which hair cells are stimulated more often?
hair cells closer to where vibrations are displaced in the scala media
sound localization is based on
interaural intensity and time differences
What is the first stop of the neural pathway of sound transduction?
vestibulocochlear nerve
Conduction deafness
sound waves not conducted from outer to inner ear
What may cause conduction deafness?
earwax buildup, fluid in middle ear, damage to eardrum, bone overgrowth in middle ear
What frequencies does conduction deafness impair?
all
How can conduction deafness be helped?
earing aides
Sensorineural/perceptive deafness
nerve impulses are not conducted from the cochlea to the auditory cortex
What causes sensorineural/perc deafness?
damaged hair cells from loud noises
What frequencies are affected by s/p deafness?
only particular frequencies where haircells are damaged
How can S/P deafness be helped?
cochlear implants
Presbycusis
age-related hearing impairment
After scala vestibuli is displaced, sound travels across the _____ and down into the ____
vestibular membrane; cochlear duct
At the cochlear duct, sound passes through ____ to reach the _______ membrane
endolymph; basilar
Passing through the basilar membrane, sound reaches ______ of the scala ________ and travels out of the cochlea via the ______
perilymph; tympani; round window
How does place theory explain nerve transduction of sound?
the physical differentiation of hair cell stimulation acts as a neural code for pitch discrimination
According to place theory, how can similar pitches be differentiated?
via the magnification effect produced by outer hair cells
What parts of the brainstem are stimulated by the vestibulocochlear cranial nerve VIII?
the medulla oblongata, pons and the inferior colliculi
Where in the thalamus do nerve impulses from sound pass?
through the medial geniculate body
Where in the cortex do auditory signals go for interpretation?
to the auditory cortex of the temporal lobe
How does the auditory cortex break down sound interpretation?
it is tonotropic, in that different areas of the auditory cortex process different sound frequencies
What happens once K+ in released into endolymph from stereocilia stimulation?
depolarization and release of glutamate NT at the synapse with sensory neurons
When the AP completes, K+ of the endolymph returns to ______ at the base of _____cilia
perilymph; stereo
