PSIO 201 5th Edition Lecture 38 Outline of Last Lecture The EyeOutline of Current Lecture I. Auditory EarII. Hair CellsIII. TransductionIV. Gravity and AccelerationV. Balance and EquilibriumCurrent LectureExternal (Outer) Ear – - external auditory canal- auricle- tempanic membraneMiddle Ear-- Auditory Ossicles- Auditory tubeInternal (Inner) Ear- - Utricle- Cochlea- Semicircular ducts (balance and equilibrium)- Saccule (Gravity and acceleration) Hearing : Structural Issue 1. Sound wave arrives at tympanic membrane2. Vibration moves auditory ossicles3. Stapes depresses oval window, generates pressure wave in cochlear ducts4. Pressure wave distorts membrane5. Vibration of basilar membrane excited overlying hair cells ( produces receptor potentials)Hair Cells – Stereocilia – common receptor for hearing and balanceMechanically-gated channels in stereocilia membrane open- cations (K+) enter depolarization Bending stereocilia pulls open the gates of ion channelsSummary of Auditory Transduction:1. Vibration of basilar membrane at different places depending on pitch2. Movement of stereocilia on hair cells3. Opening of mechanically gated channels4. Movement of K+ into hair cells causes depolarization ( remember, endolymphoutside of hair cells is high in K+)5. Depolarization causes opening of Ca++ channels at base of hair cells6. 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 cellsGravity and Acceleration – involves patterns of hair cell activation in the Ultricle and SacculeOtoliths – gravity presses down; generating receptor
View Full Document
Unlocking...