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Chapter 27 - Hearing
Book chapter

Chapter 27 - Hearing

The Laboratory Fish, pp.480-487
Academic Press
2000
DOI: 10.1016/B978-012529650-2/50036-6

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Abstract

This chapter deals with the mechanosensory transducers of the various sensory organs, the hair cells, as well as the afferent and efferent connections of these sensory epithelia that provide the basis for acquisition of distinct stimuli by the brain. Hair cells are the universal mechano-electric transducers of the inner ear and the lateral line of vertebrates. All hair cells share an apical specialization consisting of numerous protrusions of variable length. During development, all mechanosensory hair cells form from specialized embryonic tissue, the placodes. Hair cells also provide neurotrophic support for the developing sensory neurons and the sensory neurons degenerate in the absence of this support. The sensory epithelia of the semicircular canals, called crista ampullaris, are an aggregation of hair cells situated in an enlargement of each canal, the ampulla. A crista is typically covered by a gelatinous cupula and is composed of various forms of hair cells that are all polarized in one direction only. Variation of the crista hair cells concerns the length and size of the apical stereocilia which provide the physical basis for hair cells of variable sensitivity. An additional system common to all mechanosensory hair cells are neurons in the brainstem which terminate with their axons either on the hair cells or on afferent fibers which innervate hair cells.

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