class+23+lecture+_vestibular2__posted

class+23+lecture+_vestibular2__posted - Sensation and...

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Sensation and Perception Class XXIII: Vestibular System & Wrap Up
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Figure 15.6 The vestibular apparatus
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Peripheral Structure of the Mammalian Vestibular System Hair cell responses In the absence of stimulation, hair cells release neurotransmitter at a constant rate When hair cell bundles bend, change in hair cell voltage is proportional to the amount of deflection § Bending toward tallest stereocilia causes depolarization § Bending away from tallest stereocilia causes hyperpolarization Hair cells increase firing to rotation in one direction and decrease firing to rotation in the opposite direction
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Figure 15.7 Hair cell responses
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Peripheral Structure of the Mammalian Vestibular System Semicircular canals Each one is about three-fourths of a toroid (donut) shape, measuring 15 mm long and 1.5 mm in diameter § Canals are filled with a fluid called perilymph A second, smaller toroid is found inside the larger toroid, measuring 0.3 mm in diameter § Formed by a membrane filled with fluid called endolymph Cross section of each canal swells substantially near where the canals join the vestibule: Ampulla
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Figure 15.8 The semicircular canals
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Peripheral Structure of the Mammalian Vestibular System Semicircular canals (cont’d) Within the endolymph space of each ampulla is the crista Cristae : The specialized detectors of angular motion located in each semicircular canal in a swelling called the ampulla § Each crista has about 7000 hair cells and associated supporting cells and nerve fibers § Cilia of hair cells project into a jellylike cupula that forms an elastic dam extending to the opposite wall of the ampulla, with endolymph on both sides of the dam When the head rotates, the inertia of the endolymph causes it to lag behind, leading to tiny deflections of the hair cells
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Peripheral Structure of the Mammalian Vestibular System Coding of direction in the semicircular canals Three semicircular canals in each ear Each canal is oriented in a different plane Each canal is maximally sensitive to rotations perpendicular to the canal plane
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Figure 15.9 Each semicircular canal is maximally sensitive to rotations perpendicular to the canal plane
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Peripheral Structure of the Mammalian Vestibular System Push–pull symmetry Hair cells in opposite ears respond in a complementary fashion to each other When hair cells in the left ear depolarize, those in the analogous structure in the right ear hyperpolarize
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Figure 15.10 The semicircular canals function in pairs that have a push–pull relationship
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This note was uploaded on 11/17/2011 for the course PSYCHOLOGY 830:301 taught by Professor Staff during the Spring '10 term at Rutgers.

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class+23+lecture+_vestibular2__posted - Sensation and...

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