PSIO 201 5th Edition Lecture 38 Outline of Last Lecture The Eye Outline of Current Lecture I Auditory Ear II Hair Cells III Transduction IV Gravity and Acceleration V Balance and Equilibrium Current Lecture External Outer Ear external auditory canal auricle tempanic membrane Middle Ear Auditory Ossicles Auditory tube Internal Inner Ear Utricle Cochlea Semicircular ducts balance and equilibrium Saccule Gravity and acceleration Hearing Structural Issue 1 2 3 4 5 Sound wave arrives at tympanic membrane Vibration moves auditory ossicles Stapes depresses oval window generates pressure wave in cochlear ducts Pressure wave distorts membrane Vibration of basilar membrane excited overlying hair cells produces receptor potentials Hair Cells Stereocilia common receptor for hearing and balance Mechanically gated channels in stereocilia membrane open cations K enter depolarization Bending stereocilia pulls open the gates of ion channels Summary of Auditory Transduction 1 Vibration of basilar membrane at different places depending on pitch 2 Movement of stereocilia on hair cells 3 Opening of mechanically gated channels 4 Movement of K into hair cells causes depolarization remember endolymph outside of hair cells is high in K 5 Depolarization causes opening of Ca channels at base of hair cells 6 Ca triggers exocytosis of neurotransmitter and depolarization of underlying sensory neurons in VIII nerve Equilibrium and Balance semicircular ducts within canals 3 ducts anterior posterior lateral provide axes Ampulla complex 3D movements of hear can be coded for by the various patterns of Aps that arise from the hair cells Gravity and Acceleration involves patterns of hair cell activation in the Ultricle and Saccule Otoliths gravity presses down generating receptor potential
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