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Transcript 
MEDS 371
Peripheral Auditory System
Dr. Duck O. Kim
dB: decibel
SPL: sound pressure level
dB SPL = 20 log10 (pressure/ref)
ref = 20 mPa
frequency (Hz)
audible freq. range for humans: approx. 20 ~ 20,000 Hz
Davis & Silverman, 1970
dB SPL re 20 mPa
threshold of hearing
Purves
Fig 13.4
Purves
Fig 13.3
the middle ear
Impedance
transformation
middle-ear muscles:
tensor tympani - malleus
stapedius - stapes
Pickles,
Pickles,1988
1988
Bekesy, 1960
external ear
middle ear
inner ear
bas. mem. disp. amplitude
data from
human
cadavers
origin of
tonotopic
organization
Bekesy, 1960
distance from stapes (mm)
cochlea
SV
ST
temporal bone
Pickles, 1988
inner ear
Purves
fluid in ST & SV: perilymph (like CSF)
fluid in SM: endolymph (high K+)
cochlear partition
SV
RM
SM
TM
ST
BM
Smith,
1975
inner hair cell
outer hair cell
afferent
afferent
*
*
Smith, 1975
tip-link model of hair-cell excitation
Pickles, 1984
Purves, Fig 12-8;
adapted from
Lewis & Hudspeth,
1983
Purves
Fig 13-6
threshold (dB SPL)
frequency tuning curves
cochlear
neuron
basilar
membrane
Sellick et al, 1982
Neely & Kim, 1983
frequency (kHz)
frequency tuning curves of cochlear neurons
threshold (dB SPL)
OHC damage
normal
Robertson &
Johnstone,
1979
frequency (kHz)
mammalian cochlear OHC
HB motility
somatic
motility
OHC motilities
underlie
the cochlear
amplifier.
Kim, 1986
Innervation of IHCs and OHCs by cochlear neurons
adapted from Spoendlin, 1972
Phase-locked discharges of a cochlear nerve fiber
Stimulus: 300 Hz pure tone
Evans, 1975
two codes
of frequency
in auditory
nerve fibers
val
discharge rate (spikes/s)
coding of sound intensity
increase of sound intensity ->
(1) increase of discharge rates of
cochlear nerve fibers (with low
spontaneous rates);
(2) increase of number of excited
cochlear nerve fibers
Kim et al., 1991
distance along cochlea
hearing loss
examples_____
conductive hearing loss
otosclerosis
otitis media
impaction of ear canal
sensorineural hearing loss
acoustic trauma
ototoxic drugs
Meniere’s disease
mixed hearing loss
presbycusis
Purves Box 13-C
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