8.5 hearing Flashcards
3 ossicles?
malleus
incus
stapes
dwscribe the pathway of the sound until oval window
oval window -> scala vestibuli -> helicotrema -> scala tympani -> round window
where does the organ of corti located?
in the scala media
describe sound
longitudinal wave
330 m/s
describe pure tone
single frequency
sinusoid wave
not normally produced in nature
dwscribe the intensity of sound
determined by the amount of pressure, measured by dB
how can we measure dB?
dB= 20xlog(actual pressure/reference pressure)
what does the referance pressure equal to?
20 microPascals
what is the purpose of the middle ear? how?
increase in the intensity of sound
bcs oval window is 10-20 times smaller than tympanic membrane
describe the structure of hair cells-
modified eputhelial cells with stereocilia on the apical surface.
what happens to the hair cells apon stimulation?
they secrete Glu on their basal side
what causes the stereocilia to bend?
what will happen then?
mechanical stimulus
causes channels to open -> potassium influx -> depol -> VGCaC open -> Glu exocytosis -> AP
which hair cells are the primary auditory R?
inner hair cells
where can we find the perilymph?
scala tympani + scala vestibuli
K
Na
conc in the perilymph?
K- 2 nM
Na- 140 nM
endolymph K and Na conc
K- 150 nM
Na- 1 nM
what produces the endolymph? and where?
by the stria vascularis
in the cochlea
what is the difference in voltage btw endolymph and membrane potential of the hair cells?
endolymph: +80 mV
hair cells: -40 mV
why is the large electrochemical gradient btw endolymph and hair cells important?
bcs both contain a lot of potassium
so we need another help in generating a difference btw them that will lead to charge difference! so K ions will be driven from the endolymph to the hair cells
what family does the channel on stereocilia belong to?
Transiant Receptor Potential (TRP) A1 family
describe the Transiant Receptor Potential (TRP) A1
nonspecific cation channels
what does contraction of the outer hair cells require?
Prestin
it is a motor protein
does not need ATP
where will the higher frequency sound reach in the chochlea?
not far away. only low frequency will reach the apex
Broadmann area?
40/41
