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Auditory System: Cochlea<br />
NEUROPHYSIOLOGY<br />
A. Membranous<br />
labyrinth within<br />
bony labyrinth<br />
(path of sound<br />
waves)<br />
Cochlear nerve<br />
Utricle<br />
Saccule<br />
Semicircular<br />
canals<br />
Scala vestibuli<br />
Cochlear duct<br />
(scala media)<br />
Scala tympani<br />
B. Section<br />
through turn<br />
of cochlea<br />
Efferent<br />
nerve fibers<br />
Afferent<br />
nerve fibers<br />
Spiral ganglion<br />
Round window<br />
Scala vestibuli<br />
(perilymph);<br />
weakly<br />
positive +80 mV<br />
Scala tympani<br />
(perilymph); 0 mV<br />
Oval window and stapes<br />
Vestibular (Reissner’s)<br />
membrane<br />
Cochlear duct (scala media;<br />
endolymph)<br />
Tectorial membrane<br />
Spiral ligament<br />
Bone<br />
Outer hair cells; 60 mV<br />
Basilar membrane<br />
Inner hair cell; 60 mV<br />
C. Spiral organ<br />
of Corti<br />
Hair cells<br />
Inner Outer<br />
Tectorial membrane<br />
Stereocilia<br />
Rods<br />
and<br />
tunnel<br />
of Corti<br />
Basilar membrane<br />
Supporting cells<br />
Spiral lamina Afferent nerve fibers<br />
Spiral ganglion<br />
Efferent nerve fibers<br />
As basilar membrane moves up, hairs are deflected outward, causing<br />
depolarization of hair cells and increased firing of afferent nerve fibers<br />
©<br />
FIGURE 2.34<br />
COCHLEAR RECEPTORS •<br />
The cochlea transduces sound into electrical signals. This is<br />
accomplished by the hair cells, which depolarize in response to<br />
vibration of the basilar membrane. The basilar membrane moves in<br />
response to pressure changes imparted on the oval window of the<br />
cochlea in response to vibrations of the tympanic membrane.<br />
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