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Purves D, Augustine GJ, Fitzpatrick D, et al., editors. Neuroscience. 2nd edition. Sunderland (MA): Sinauer Associates; 2001.

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Neuroscience. 2nd edition.

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Vestibular Hair Cells

The vestibular hair cells, which, like cochlear hair cells, transduce minute displacements into behaviorally relevant receptor potentials, provide the basis for vestibular function. Vestibular and auditory hair cells are quite similar; a detailed description of hair cell structure and function has already been given in Chapter 13. As in the case of auditory hair cells, movement of the stereocilia toward the kinocilium in the vestibular end organs opens mechanically gated transduction channels located at the tips of the stereocilia, depolarizing the hair cell and causing neurotransmitter release onto (and excitation of) the vestibular nerve fibers. Movement of the stereocilia in the direction away from the kinocilium closes the channels, hyperpolarizing the hair cell and thus reducing vestibular nerve activity. The biphasic nature of the receptor potential means that some transduction channels are open in the absence of stimulation, with the result that hair cells tonically release transmitter, thereby generating considerable spontaneous activity in vestibular nerve fibers (Box B). One consequence of these spontaneous action potentials is that the firing rates of vestibular fibers can increase or decrease in a manner that faithfully mimics the receptor potentials produced by the hair cells.

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Box B

Adaptation and Tuning of Vestibular Hair Cells.

Importantly, the hair cell bundles in each vestibular organ have specific orientations (Figure 14.2). As a result, the organ as a whole is responsive to displacements in all directions. In a given semicircular canal, the hair cells in the ampulla are all polarized in the same direction (Figure 14.2C). In the utricle and sacculus, a specialized area called the striola divides the hair cells into two populations with opposing polarities (Figures 14.2C; see also Figure 14.4C). The directional polarization of the receptor surfaces is a basic principle of organization in the vestibular system, as will become apparent in the following descriptions of the individual vestibular organs.

Figure 14.2. The morphological polarization of vestibular hair cells and the polarization maps of the vestibular organs.

Figure 14.2

The morphological polarization of vestibular hair cells and the polarization maps of the vestibular organs. (A) A cross section of hair cells shows that the kinocilia of a group of hair cells are all located on the same side of the hair cell. The arrow (more...)

Figure 14.4. Morphological polarization of hair cells in the utricular and saccular maculae.

Figure 14.4

Morphological polarization of hair cells in the utricular and saccular maculae. (A) Cross section of the utricular macula showing hair bundles projecting into the gelatinous layer when the head is level. (B) Cross section of the utricular macula when (more...)

By agreement with the publisher, this book is accessible by the search feature, but cannot be browsed.

Copyright © 2001, Sinauer Associates, Inc.
Bookshelf ID: NBK11037

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