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BIOLOGY 2C03 (138)
Kim Dej (45)
Lecture

Hair Cells

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Department
Biology
Course Code
BIOLOGY 2C03
Professor
Kim Dej

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Description
Outline of Lecture 56 (03-24 A; Fuchs) Hair Cells I. Introduction to hearing - Sound is a pressure wave, and pure tones can be characterized by amplitude (measured indirectly as dB) and frequency - Dynamic range of hearing in humans is about 0-100 dB (whisper to pain) and 20-20,000 Hz - Types of damage to ear - Chronic severely loud sound exposure kills hair cells - Ototoxic antibiotics, e.g. streptomycin or gentamicin, kills hair cells - Hearing loss of high frequencies with age, aka presbycusis I. Anatomy of the ear A) Outer ear - Pinna: funnels and amplifies sound, sound shadows provide resolution of sound origin - External auditory canal: acts as resonant tube for 4 kHz tones B) Middle ear - Impedance matching of air to water sound transmission by two mechanisms (1) Lever advantage of ossicles (malleus, incus, stapes) (2) Oval window of stapes is smaller than eardrum - Middle ear muscles (tensor tympani, stapedius): restrict ossicle movement in response to loud sound to prevent damage - Damage in the middle ear is called “conductive” C) Inner ear (more on cochlea below) - Damage in the inner ear is called “sensorineural” III. The Cochlea - Memorize cochlear structure (e.g. figure on p. 5) - Stereocilia of hair cells are arranged in rows of increasing height and are embedded in the tectorial membrane; shear of basilar membrane WRT tectorial membrane causes displacement of hair bun
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