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Unformatted text preview: nals- detect rotational acceleration or deceleration in any direction. Otolith organs- detect linear acceleration Detect changes in rate of linear movement in any direction. Provide information important for determining head position in relation to gravity, • Equilibrium • Neural signals generated in response to mechanical deformation of hair cells by specific movement of fluid and related structures. • Vestibular input goes to vestibular nuclei in brain stem and to cerebellum for use in maintaining balance and posture, controlling eye movement, perceiving motion and eye orientation. • • Semicircular canals- hair cell bundles are aligned in mirrored orientation. Rotation depolarizes one set of hair cells and hyperpolarizes the cells in the opposite semicircular canal. • • • • • • • • The response is similar to that in auditory hair cells Stereocilia bending toward the kinocilium: depolarizes’ Steriocelia bending away form the kinocelium: hyperpolarizes Two structures most important in eye’s refractive ability Cornea- contributes most extensively to eye’s total refractive ability. Refractive ability remains constant b/c curvature never changes. Lens Refractive ability can be adjusted by changing curvature as needed for near or far vision. • • • • • Accommodation (Focus) Change in strength and shape of lens Accomplished by actions of ciliary muscle and suspensory ligaments. Age-related reduction in accommodation ability. Retina • • • • • • • • • Receptor containing portion of the eye Actually an extension of the CNS Neural portion of retina consists of three layers of excitable cells Outermost layer containing rods and cones. Middle layer of bipolar cells Inner layer of ganglion cells Axons of ganglion cells join to form optic nerve Point on retina at which optic nerve leaves in the optic disk. Region is often called the blind spot b/c no image can be detected here b/c of lack of rods and cones. • • • • • • Photoreceptors Rods...
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- Spring '10