動物生理学 III①Handout No. 12②Figure 40-1 The vestibular labyrinth.
A. Location of vestibularand cochlear divisions ofthe inner ear with respect
to the head. B. The inner
ear is divided into bonyand membranous labyrinths. The bony labyrinth
is bounded by the petrous portion of the temporalbone. Lying within thisstructure is the membranous labyrinth, whichcontains the organs ofhearing (the cochlea) andequilibrium (the utricle,saccule, and semicircularducts). The space between bone and membrane is filled with perilymph, while the membranous labyrinth is filledwith endolymph. Sensory
cells in the utricle, saccule, and the ampullae ofthe semicircular ducts
respond to motion of thehead. (Adapted fromlurato 1967.)

Figure 37.5 A model of adaptation by hair cells. A hair bundle
may be subjected to prolonged deflection in the positive ornegative direction. The electrical response to a positive stimulus
displays an initial depolarization, followed by a decline to a plateau
and an undershoot at the cessation of the stimulus. Negative
stimulation elicits a complementary response: The receptor
potential largely abates during stimulation but shows a rebound at
the end. Bundle movement in response to positive stimulation
increases tip link tension and opens transduction channels. As
stimulation continues, however, the tip link's upper attachment
moves down the stereocilium, allowing each channel to close
during adaptation. During negative stimulation tension is restored
to the initially slack tip link by active ascent of the link's upper
insertion.

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Figure 40-2 Hair cells in the vestibular labyrinth transduce mechanical stimuli into
neural signals. At the apex of each cell is a hair bundle in which a number of stereocilia
taper in length toward a single kinocilium. The membrane potential of the receptor celldepends on the direction in which the hair bundles bent. Deflection toward the kinocilium
causes the cell to depolarize and thus increases the rate of firing in the afferent fiber.
Rending away from the kinocilium causes the cell to hyperpolarize, thus decreasing theafferent firing rate. (Adapted from Flock 1965.)⑤Figure 40-3 The utricle is organized to detect tilt of the head. The hair cells inthe epithelium of the utricle have apical hair bundles that project into the otolithic
membrane, a gelatinous material embedded with calcium carbonate stones(otoconia). The hair bundles are polarized, but not all cells are oriented in thesame direction. The response of an individual hair cell in the utricle to a tilt of thehead depends on the direction in which its hairs are bent by the gravitational
force of the otoliths. When the head is tilted in the direction of the axis of polarity
for a particular hair cell, that cell depolarizes and excites the afferent fiber. Whenthe head is tilted in the opposite direction, the hair cell hyperpolarizes and inhibits
the afferent fiber (see Figure 40-2). (Adapted from lurato 1967.)

Figure 40-5 The organization of the ampulla of a semicircular canal.
A. A thickened zone of epithelium, the ampullary crista, contains the hair cells. The
hair bundles of the hair cells extend into a gelatinous diaphragm called the cupula,which stretches from the crista to the roof of the ampulla.
B. The cupula is displaced by the flow of endolymph when the head moves. As aresult, the hair bundles extending into the cupula are also displaced.