Lecture 10 Notes F09

Lecture 10 Notes F09 - PSYCH 301 LECTURE 10 Audition I....

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PSYCH 301 LECTURE 10 Audition I. Audition. A. Sounds: the basis of audition.   1. Sound   waves   are   produced   by   the   vibrations   of   air  molecules, changes in air pressure that stimulate specialized organs.  The sine- wave form of these vibrations has particular characteristics: a. Amplitude :  loudness b. Frequency :  pitch c. Complexity :  timbre 2. Few sounds are pure, simple combinations of sine waves;  most are complex and mixed together.  Fourier analysis  is the scientific method  of breaking down complex waveforms into component sine waves.  B. Mechanisms of audition :   1. Gross anatomy of audition :   a. The outer ear :   The outer ear acts as a funnel to  project sound vibrations into the auditory meatus, down the   auditory canal  where it strikes the  tympanic membrane  (the eardrum). b. The   middle   ear :     vibrations   of   the   tympanic  membrane   are   transferred  to   the   ossicles   (the  ear   bones).     The  tympanic  membrane is attached to the malleus, the incus, the stapes, and then to the oval  window, the membrane separating the middle ear from the inner ear.   These  bones improve the transfer of energy to the inner ear.
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c. The inner ear :   the   cochlea , a snail-shaped organ.  Vibrations of the oval window create waves of particular frequencies in the  basilar membrane   of the cochlea; this stimulates the   hair cells   at particular  locations along the basilar membrane by forcing them against the   tectorial  membrane .  There are 3 rows of outer hair cells and 1 row of inner hair cells.  This portion of the cochlea is called the   organ of Corti . Auditory nerve fibers  synapse at the bottoms of the hair cells and project away from the cochlea  collecting together to form the auditory nerve. d. Hair   cells   are   so   named   because   on   their   apical  surface, fixed to the tectorial membrane is a bundle of  cilia  filled with a parallel  array of cross-bridged actin filaments.   Adjacent cilia are connected by elastic  filaments,   tip links , at points of attachment called   insertional plaques .   Ion  channels (TRPA1, a transient receptor potential cation channel; similar receptors  mediate other perceptions) are located in the insertional plaques, such that  deflection of the basilar membrane bends the cilia, stretches the tip links and 
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This note was uploaded on 02/26/2011 for the course PSYC 301 taught by Professor Yager during the Spring '10 term at Maryland.

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Lecture 10 Notes F09 - PSYCH 301 LECTURE 10 Audition I....

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