Download Ch 15b Hearing and Equilibrium

Ch 15b Hearing and Equilibrium
Ear anatomy
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external ear
external acoustic canal
tympanic membrane
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middle ear
3 ossicles
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inner ear
• malleus
• incus
• stapes
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cochlea
hearing
vestibule
equilibrium
semicircular canals
equilibrium
HEARING
cochlea anatomy
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cochlear duct
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fluid filled membrane
fluid
endolymph
receptor
Organ of Corti = spiral organ
2 fluid filled chambers :
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fluid
perilymph
scala vestibuli
contacts oval window
scala tympani
contact round window
Organ of Corti
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= spiral organ
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receptors for hearing
within cochlear duct
basilar membrane
support
hair cells
receptor cells
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stereocilia
extensions into tectorial membrane
tectorial membrane
covers stereocilia ; stationary
Sound
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sound is a vibration
waves of vibrating air (or any medium)
physics terms
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frequency
# waves per second
wavelength
distance betw crests
amplitude
pitch
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height of each wave
different frequency
20 to 20000 Hz
1500 – 4000 Hz
most sensitive range
low pitch :
low frequency ; large wavelength
loudness
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hertz (Hz)
0 dB
decibels (dB)
amplitude
lowest audible sound
> 120 dB very painful
hearing
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GOAL = depolarize the receptor cells
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open Na channels
How?
stretch their hair
path of vibration
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air
tympanic membrane
ossicles
oval window
perilymph
(scala vestibuli)
endolymph (cochlear duct)
basilar membrane
hair cells
transmission of sound / vibration
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sound wave (air) vibrates tympanic membrane
3 ossicles amplify the vibration
stapes vibrates the oval window
oval window vibrates perilymph
perilymph vibrates endolymph
endolymph vibrates basilar membrane
basilar membrane vibrates hair cells
excitation of receptor cells
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organ of Corti
basilar membrane vibrates hair cells
stereocilia stretch against tectorial membrane
open K channels
K+ (in endolymph) rushes into cell
hair cells depolarize
hair cells release NT
Pitch
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varied thickness of basilar membrane
responds to different frequency
frequency ~ pitch
multiple pitches possible
specific areas of auditory cortex
auditory processing
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pitch
loudness
localization
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number of hair cells stimulated
where is sound coming from
compares both ears
• intensity
• timing
auditory pathway
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to temporal lobe
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cochlear nerve
spiral ganglion
cochlear nuclei
thalamus
temporal lobe
to inferior colliculi
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auditory reflex
to cerebellum
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olivary nuclei
problems
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deafness
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conduction deafness
neural deafness
tinnitus
Meniere’s syndrome
hearing loss
tinnitus
vertigo
EQUILIBRIUM
equilibrium anatomy
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2 structures :
vestibule
semicircular canals
static equilibrium
(linear)
dynamic equilibrium (rotation)
receptors
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vestibule
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macula
hair cells
otoliths
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semicircular canals
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ampula
hair cells
cupula
excitation of macula
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position change moves otoliths
otoliths bend sterocilia
hair cells depolarize
only respond to change of position, movement
excitation of ampulla
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rotation moves endolymph
endolymph deforms cupula
cupula bends sterocilia
equilibrium pathway
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hair cells
vestibular nerve
vestibular nuclei
medulla
cerebellum
reflex movement
cerebrum
parietal lobe
conscious awareness of position and movement
problems
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motion sickness
vertigo
nystagmus