Auditory System Flashcards
what is sound?
waves of compressed and expanded air, usually in the form of vibrations
loudness is determined by
magnitude of pressure differences (wave amplitude)
pitch is determined by
speed at which pressure changes (wave frequency)
air molecules get ___ at higher pressure areas of the ear
compressed
what is the approximate sound range for humans?
2-20000Hz
humans can detect sound of ___ frequency ranges
4
what is the function the outer and middle ear?
amplify sound
what is the external structure of the ear called? what is its function?
Pinna; funnelling sound onto tympanic membrane
what is the function of the external auditory canal?
funnel sound onto tympanic membrane
when sound reaches the tympanic membrane, what happens to it?
starts to vibrate
vibration of the tympanic membrane causes the movement of __
auditory ossicles
what are the middle ear bones (auditory ossicles? )
malleus, incus, stapes
what separates the outer from middle eat
the tympanic membrane
the movement of the ossicles causes amplification of sound so that when it reaches the oval window, it is __X louder than it was at the tympanic membrane
20
what causes the amplification of sound by the ossicles?
their leverage
tympanic vibrations are very dependent of __balance between middle and outer ear
pressure
how can pressure balance be restored when in a plane and the pressure in the middle ear is too high?
swallowing, because of the Eustachian tube that connects the throat to the middle ear will relive the pressure
vibrations of the oval window cause pressure waves of ___ in the ___ to the__ and onto the ___
perilymph in the scala vestibuli; scale tympani; round window
pressure waves deform the walls of the __ and cause pressure waves in the ___, which falls the ___ duct
scala vestibuli, endolymph, cochlear
pressure waves in the endolymph lead to vibrations of the ___ membrane, and different parts may move depending on __
basilar; sound pitch (frequency of waves)
what is the cochlea?
complex set of fluid-filled ducts
what are the 2 labyrinths of the cochlea?
bony and membranous
what fluid is contained in the bony labyrinth?
perilymph
what fluid is contained in the membranous labyrinth?
endolymph
the endolymph is rich in what ion?
K+
the two membranes that separate the 2 labyrinths are
vestibular and basilar membrane
what are the 2 ducts of the bony labyrinth?
- scala vestiboli
2. scala tympani
what is the 1 duct of the membranous labyrinth?
- cochlear duct
vibration of the basilar membrane causes bending of __
stereocillia
stereocillia contain ___ gated ion channels connected __
mechanically; tip-link proteins
t/f bending of stereocillia can either open or close mechanically gate ion channels
true
when mechanically gated ion channels are opened, ___ rushes in, causing __
K+; depolarization
membrane depolarization causes the influx of __ ions and graded release of __
ca2+ ; NT glutamate
release of glutamate depolarizes the ___ which causes __
primary sensory neuron; action potential
hair cells pert rude into the __
endolymph
resisting on the basilar membrane is the ___ which contains inner ___ cells that act as ___
organ of corti; hair; sensory receptors
the stereocillia of hair cells are embedded in the ___
tectorial membrane
hair cells are contacted by the dendrites of ___ neurons
primary sensory neurons
___ determines which hair cells depolarize
sound pitch
high-pitch sounds activate hair cells at the __ of the cochlea
base
low-pitch sound activate hair cells at the __ of the cochlea
apex
___ determines the amount of hair cell depolarization, glutamate release and action potential frequency of first order auditory neutron
sound amplitude (loudness)
auditory pathways are __
polyneuronal
auditory pathways have relays in the ___, ___ and ___ before termination in the ___
brainstem (cochlea nuclei, inferior livery nucleus), midbrain (interior colliculus) and thalamus (medial geniculate nucleus), primary auditory cortex
the inferior olivary nucleus is important to ___
sound localization
the inferior olivary nucleus detects timing changes in ___ arriving at the 2 ears
action potential
the primary auditory cortex is located in the __ lobe
temporal
the primary auditory cortex is responsible for __
conscious awareness of sound
information from the base and apex of the cochlea reaches ___ sides of the auditory cortex (___ organization)
opposite ; topographical
higher order sound processing is done in the
auditory association area
sounds from the base of the cochlea go to the __ part of the auditory cortex
medial
sounds from the apex of the cochlea go to the __ part of the auditory cortex
lateral
the vestibular apparatus is part of the __
labyrinth
what is the vestibular apparatus?
series of fluid-filled tubes in the inner ear (sometimes groups with cochlea as part of labyrinth)
what are the 2 main components of the vestibular apparatus?
- semicircular canals
2. otolith organs
what is the fluid the vestibular apparatus?
same endolymph as cochlea
what are the 2 otolith organs?
utricle and the saccule
what is the function of the vestibular apparatus?
detection of rotational and linear accelerations of the head
what is the function of the semicircular canals?
detect rotational acceleration along 3 perpendicular axes
semicircular canals have hair cells in the ___ and stereocillia in the __
ampullae; cupula
what are the cupola of the semicircular canals?
gelatinous mass
what are the ampullae of the semicircular canals?
bulges
what happens in the inner ear when the head rotates?
- endolymph puts pressure on cupola, bending stereocillia, cation channels are opened or closed depending on direction of rotation, hair cells are either de- or hyper polarized, increase or decrease in NT and frequency of AP
the otolith organs detect ___
horizontal accelerations of head in horizontal or vertical directions
the utricle responds to accelerations in the __ plane
horizontal
the saccule responds to accelerations in the ___ plane
vertical
sterecillia of hair cells in the utricle and saccule are ensheathed in a ___ substance containing ___
gelatinous (otolith membrane) ; otoliths
otoliths respond to ___ force and cause ___ of hair cells cilia
gravitational
