456
UNIT THREE
Branch of
cochlear
nerve
Scala vestibuli
(contains perilymph)
Scala tympani
(contains perilymph)
Cochlear duct
(contains endolymph)
Spiral organ (organ of Corti)
Hair cells
Supporting
cells
Basilar
membrane
Nerve
fibers
Branch of
cochlear nerve
Tectorial
membrane
Vestibular membrane
Basilar membrane
(a)
(b)
FIGURE 12.13
±Cochlea.±(
a
) Cross section of the cochlea. (
b
) Spiral organ and the tectorial membrane.
ion channels open and its cell membrane depolarizes. The
membrane then becomes more permeable, specif
cally to
calcium ions. The receptor cell has no axon or dendrites,
but it does have neurotransmitter-containing vesicles in
the cytoplasm near its base. In the presence oF calcium
ions, some oF these vesicles Fuse with the cell membrane
tectorial membrane. Other Frequencies defl ect other sets oF
receptor cells.
Hearing receptor cells are epithelial cells, but they
respond to stimuli somewhat like neurons (see chapter 10,
pp. 365–370). ±or example, when a receptor cell is at rest,
its membrane is polarized. When its hairs bend, selective
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