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Lecture 1

BIOL 2213 Lecture 1: Phys10:6

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BIOL 2213

Slide 36: Stapes inserted into cochlea (formed by bone), inner tube inside cochlea = cochlear duct Both tubes are full of fluid: endolymph and perilymph Endolymph = inside the cochlear duct Perilymph = outside; in the scala tympani and scala vestibuli Distortion gets transmitted into sound Different frequencies of sound distort the basilar membrane at different locations High pitch travels the farthest because it has more energy Inner membrane: cochlear duct; filled with endolymph (fluid) Paralymph surrounds the endolymph Basilar membrane makes cochlear duct; where receptors are for sound Hair cells: mechanoreceptors – when they get distorted they can change their membrane potential and generate an action potential about sound that goes to the brain Slide 38: Organ of corti: will get disturbed from pressure, causes basilar membrane to move up and down Hair cells: receptors for sound, cells that are capable of changing membrane potential in response to vibrations Cochlear nerve transmits information about sound to the brain Tectorial membrane: when basilar membrane vibrates up and down from pressure wave, stereocilia (tips of hair cells) push up tectorial membrane – starts sound going to auditory cortex Inner hair cells: responsible for picking up sound information and sending it to the brain; stereocilia not embedded in the tectorial membrane Outer hair cells: stereocillia are embedded in the tectorial membrane, regulate movement of tectorial memrbane and basilar membrane Slide 39: Purple: hair cells Extensions off surface of cell = stereocillia = elaborate mechanoreceptor cell; tips can move in either direction Bends towards tallest stereocillia = depolarizes Bends towards shorted stereocillia = repolarizes Bend back and forth releasing neurotransmitter Issue: there’s different qualities of sound (frequency and amplitude) Frequency: deals with pitch – depends on how far up the basilar membrane is distorted (close to helicotrema or farther away) – higher frequency causes distortion of basilar membrane close to round window vs. low frequency causes distortion closer to helicotrema Depolarization is due to high concentrations of potassium Potassium is actively transported out at the base of the cell Slide 41: “Rest of the inner ear” – not including the cochlea Includes: semicircular canals, ampulla, cupula Semicircular canals oriented in 3 dimensions of space so that they can detect rotational movements of the head, move in relation to the endolymph Ampulla: swelling in bone/semicircular canal; contains the cupula Cupula: inside the ampulla, made of gelatinous substance, has stereocillia of hair cells embedded in it, bends (in relation to the endolymph because of the semicircular canals) and causes change in membrane potential in the hair cells Hair cells = receptor cells (linear acceleration, position of head relative to gravity, movements of head, sound) Slide 43: Vestibular nerve: carries information on rotational movements and position of head relative to gravity to the brain Slide 44: No movement: straight up and down Movement to the tallest tip length: increases frequency of action potential, depolarization Movement towards shortest tip length: slower frequency of action potential, hyperpolarization Can tell which way your body is moving (ex: spinning clockwise) even when your eyes closed Detect which way your head is spinning based on the frequency of the action potential Slide 45: Oriented perpendicular to each other Have hair cells, sterocillia stick up into gelatinous mass Mass contains little stones (give some weight) Standing straight up: mass sitting on hair cells Bend over: gravity pulls on mas
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