Auditory System Flashcards
what is sound?
refers to change in air pressure generated by vibrating air molecules
is sound physical or chemical energy?
physical
what is sound measured in?
decibels on a log scale
parameters of sound
amplitude: loudness
frequency:pitch
what is timbre?
complexity of the sound wave or multiple frequencies combined
what would a low amplitude sound look like?
what would a high amplitude sound look like?
what would a low frequency sound look like?
what would a high frequency sound look like?
one challenge of the auditory system is…
breaking down a sound into their frequency components
the ear successfully breaks down ____ into _____ that make up a sound
waveforms, smaller sine waves
what are the 3 main challenges of teh auditory system?
- detect and code the amplitude and relevant frequencies
- dynamically modulating this process in a context specific manner
- using information for hearing and sound localization
what three parts is the ear composed of?
outer ear, middle ear, inner ear
label this diagram:
A: ear canal
B: inner ear
C: pinna
D: ear drum
E: middle ear
F: eustachian
what does the outer ear consist of?
pinna and ear canal
function of the pinna
funnels sound into the middle and inner ear (amplification) and plays a role in sound localization
the pinna ____ filters sound waves depending on the ____ of their source
differentially, elevation
frequency range for whales
20-100,000 hz
frequency range for bats
1500-100,000 hz
frequency range for humans
20-20,000 hz
frequency range for frogs
600-3,000hz
frequency range for fish
20-3,000 hz
frequency range for crickets
500-5,000 hz
frequency range for birds
Variable across species, but top
end usually well below 10,000 Hz
what does the middle ear consist of?
the ear drum (tympanic membrane) and 3 small ossicles (malleus, incus, stapes)
what does the middle ear do?
prevents reflection of sound due to resistance in air/water differences (size of ear drum and lever action)
-tranduces sound
-a little bit of amplification of sound
sounds amplified by the _____ causes vibrations of the _____
outer ear, eardrum
information is amplified through the ____ and causes the ____ to go to the ____
middle ear, vibration, inner ear
why arent sound waves sent directly to the cochlea from the outer ear?
- Sound propagates through air, but sensory receptors/cells are in an aqueous environment in the cochlea.
- The middle ear allows for the change in medium, so sound waves don’t just reflect off the cochlea.
without the middle ear, ____ of sound energy would reflect
> 99.9%
main effects of middle ear arise from:
- size of the ear drum relative to stapes (~35X)
- lever action of the ossicles
what does the level action of the ossicles allow for?
the pressure of the ossicles to be focused onto one spot, resulting in more effective vibrations to the cochlea
-> important point of control!
label this diagram:
A: malleus
B: incus
C: stapes
D: tympanic membrane
E: base of stapes in oval window
what two things is neural control of the middle ear performed by?
- trigeminal nerve
- facial nerves
trigeminal nerve
innervates the tensor tympani muscle that works to move the malleus.
facial nerves
innervate the stapedius muscle that works to move the stapes.
what do the stapedius and tensor tympani tend to do?
stiffen the eardrum and dampen the transfer of loud sound energy from the outside world.
softer sounds cause the muscles to ____ to allow more ____
relax, sound transfer
hyperacusis
increase acuity and hypersensitivity to sound, caused by lesions affecting trigeminal and facial motor output.
what does the inner ear consist of?
the cochlea
what is the cochlea responsible for?
converting sound waves into eletrical signals the brain can interpret
vibrations become ____ and are passed from the ____ into the _____
fluid pressure waves, oval window, cochlea
once fluid pressure waves are at the cochlea, what are they converted to?
nerve impulses
describe the cochlea structure
spiral structure, bisected by the cochlear parition
whats the cochlear partition?
a flexible structure that supports the basilar membrane and the tectorial membrane.
the inner ear is a ____ consisting of three parts. what are these?
bony labyrinth, the vestibule, semicircular canals (balance), and cochlea.
what is the bony labyrinth filled with?
Filled with perilymph (~CSF, low K+ compared to hair cell)
membranous labyrinth
lodged within the bony labyrinth in the inner ear and has the same general form, but is smaller.
what is the membranous labyrinth filled with?
Filled with endolymph (high K+ compared to hair cell)
what are the fluid filled compartments of the cochlea?
scala vestibuli, scala media, and scala tympani
cochlear is partitioned by:
reisners membrane and basilar membrane
reisners membrane
divides the scala vestibuli and scala media.
basilar membrane
divides the scala media and scala tympani.
label this diagram:
A: vestibular nerve
B: auditory nerve
C: oval window
D: stapes
E: round window
F: cochlea
label this diagram:
A: tunnel of corti
B: spiral ganglion
C: scala tympani
D: inner hair cells
E: basilar membrane
F: outer hair cells
G: reisners membrane
H: scala media
I: scala vestibuli
stria vascularis
a capillary loop containing numerous blood vessels, produces endolymph
transduction from mechanical to electrical energy occurs in the ____ and is performed by ____
organ of corti, hair cells
hair cells release ____ to ____ to elicit APs
glutamate, spinal ganglion cells
displacement of the basilar membrane due to sound waves causes…
displacement of hair cells in the tectorial membrane
what drives transduction?
the compression and resulting shearing forces cause the cilia to move
label this diagram:
A: tectorial membrane
B: stereocilia
C: afferent axons
D: basilar membrane
E: inner hair cells
F: tunnel of corti
G: efferent axons
H: outer hair cells
more than __ of the ___ contracts are on ____
95%, afferent (SGCs heading to cochlear nucleus), inner hair cells
more than ___ contact each _____
20 afferent fibers, inner hair cell (and no others)
more than ___ of ___ contacts are on the ____
90%, efferent (neurons from superior olivary complex), outer hair cells
T/F: the arrangement of outer hair cells in the cochlea is the same from that of inner hair cells
false, it differs.
hair cells are embedded in the
tectorial membrane
outer hair cells have how many rows?
3 or 4
inner hair cells have how many rows?
1
stereocillia
hair-like protrusions on hair cells.
kinocilium
tallest stereocillium, makes connection with the tectorial membrane
sterocillia synapse onto ____ via a _____
ganglion cells, ribbon synapse
outer hair cells have ____, where changes in ____ lead to changes in the _____
contractile ability, membrane potential, size of outer hair cells
prestin
a transmembrane molecule that has chloride-binding sites; called the molecular motor.
when the membrane is hyperpolarized what happens with prestin?
chloride ions influx into the cell, bind to prestin,l and this leads to elongation.
when the membrane is depolarized what happens with prestin?
chloride ions efflux, leaving the prestin molecule, and this leads to contraction.
when the basilar membrane moves, the cilia on outer hair cells bend towards…
the tallest stereocillia
bending towards tallest stereocilliar causes…
tip links (connection between stereocilia, open K+ channels) of the OHC hair bundle to open allowing inflow of K+ which depolarize the OHC.