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358 Chapter 10 Sensory Physiology
e The sound waveenergy is transferredto the three bonesof the
middle ear,which vibrate.
e The stapes is attached tothe membrane of the ovalwindow.
Vibrations of theoval window create fluidwaves within the
cochlea.
Sound waves strikethe tympanicmembrane andbecome vibrations.
Incus
Ear canal Malleus StapesOval
window
-+-+--\+-- Vestibularduct(perilymph)
o-f---f---- Cochlearduct(endolymph)
----:f--rrr---- Tympanicduct(perilymph)
Tympanicmembrane
Roundwindow
e Neurotransmitter releaseonto sensory neuronscreates action
potentialsthat travel through thecochlear nerve tothe brain.
G Energy from the wavestransfers across thecochlear duct into
thetympanic duct and isdissipated back intothe middle ear at
theround window .
The fluid waves push on theflexible membranes of thecochlear
duct. Hair cells bendand ion channels open,creating an electrical
signal thatalters neurotransmitter release.
FIGURE 10-20 Sound transmission through the ear
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Vestibular duct ----+-l!-,"-f'!'--+--~
Cochlear duct --+H+.F..,.
Tectorial membrane -+"+-----';"-'H---,,?.,..
Organ of Corti --+i~~/
Uncoiled\\\\\\r
,---,4~~ \\\
Vestibularduct
Cochlearduct
Organ ofCorti
Helicotrema
Roundwindow
Tympanicduct
Basilarmembrane
Bony cochlear wall
Basilarmembrane
Tympanicduct
---"'il'tm,firI'-'--" Cochlear nervetransmits actionpotentials
fromthe hair cells tothe aud itorycortex.
Tectorial ---.,.L.membrane ""'~---------
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Rod (monochromatic vision)
Optic nerve
-=--,-1----- Sclera
111~~~;gj~:-I--/,t---~-The choroid layercontains
bloodvessels.
Pigment epitheliumof retina absorbsexcess light.
Rod
Bipolar neuron
Cone
i~~~~~~i'~-~Ganglion cell(c) Light strikes the photoreceptors in
the fovea directly
because overlying neurons are pushed aside.
To opticnerve
ilI
I
Bipolarcell
RodPigment
epithelium
receptorsare organized into layers. (e) Convergence in the
retina
FIGURE QUESTION
How many rods converge onthe ganglion cell in (e)?
Drawing of photoreceptors in the fovea adapted from E. R.
Principlesof Neural Science, 3rd edition (McGraw Hill: New York,
2000).