Chapter 7 - Chapter 7: Audition, the Body Senses, and the...

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1Chapter 7: Audition, the Body Senses, and the Chemical Senses Audition The stimulus •pitch: a perceptual dimension of sound; corresponds to the fundamental frequency •hertz (Hz): cycles per second •loudness: a perceptual dimension of sound; corresponds to intensity •timbre: a perceptual dimension of sound; corresponds to complexity Anatomy of the ear •the ear detects pitch - frequency of sound vibrations - by two means. The very lowest frequencies make up the tip of the basilar membrane vibrate in synchrony with the sound vibrations; thus, these frequencies are encoded by the rate of firing of the axons that serve this region. Higher frequencies cause different portions of the basilar membrane to vibrate: the highest frequencies cause regions closest to the oval window to vibrate. •tympanic membrane: the eardrum •ossicle: one of three bones of the middle ear •malleus: the “hammer”; the first of the three ossicles •incus: the “anvil”; the second of the three ossicles •stapes: the “stirrup”; the last of the three ossicles •cochlea: the snail-shaped structure of the inner ear that contains the auditory transducing mechanisms -scala media -scala tympani -scala vestibuli •oval window: an opening in the bone surrounding the cochlea that reveals a membrane, against which the baseplate of the stapes presses, transmitting sound vibrations into the fluid within the cochlea •organ of Corti: the sensory organ on the basilar membrane that contains the auditory hair cells -basilar membrane -hair cells -tectorial membrane •hair cell: the receptive cell of the auditory apparatus •Deiter’s cell: a supporting cell found in the organ of Corti; sustains the auditory hair cells -anchor hair cell to basilar membrane •basilar membrane: a membrane in the cochlea of the inner ear; contains the organ of Corti •tectorial membrane: a membrane located above the basilar membrane; serves as a shelf against which the cilia of the auditory hair cells move •round window: an opening in the bone surrounding the cochlea of the inner ear that permits vibrations to be transmitted, via the oval window, into the fluid in the cochlea •sound is funneled by the pinna through the ear canal to the tympanic membrane (ear drum), which vibrates with the sound. Tympanic membrane sets ossicles into vibration. The malleus connects with the tympanic membrane and transmits vibrations via the incus and stapes to the cochlea, the structure that contains the receptors . Baseplate of the stapes vibrates against the membrane behind the oval window and introduces sound waves of high or low frequency into the cochlea. The vibrations cause part of the basilar membrane to flex back and forth. Pressure changes in the fluid underneath the basilar membrane are transmitted to the membrane of the
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round window, which moves in and out in manner opposite to the movements of the oval window. That is, when the baseplate of the stapes pushes in, the membrane behind the round
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Chapter 7 - Chapter 7: Audition, the Body Senses, and the...

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