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Unit 3 Sensory Systems - Part 3.docx

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University of Waterloo
BIOL 373
Heidi Engelhardt

Unit 3 Sensory Systems – Part 3 NOTE: the vestibular complex of the inner ear is the primary sensor for equilibrium! Long wavelength = low pitch Short wavelength = high pitch High frequency = high pitch Low frequency = low pitch High amplitude = loud Tympanic membrane = eardrum Transduce vibration of the tympanic membrane to a vibration of the oval window  eventually ends up moving liquid around Inner ear: vestibular apparatus + semicircular canals and the cochlea -the vestibular apparatus + semicircular canals is the sensory transducer for our sense of equilibrium! -cochlea contains sensory receptors for hearing The oval window and round window separate the fluid-filled cochlea from the air-filled middle ear Cochlea is all fluid filled The vestibular duct and tympanic duct are actually continuous (it is 1 single fluid-filled space that surrounds the blue zone: cochlear duct) Vibration sends a travelling wave of motion through the fluid and it pushes on the cochlear duct and the bottom part of the cochlear duct -round window allows pressure of vibration to dissipate (not very interesting…) -the cochlear duct (in blue) is filled with a special fluid called endolymph -tympanic and vestibular ducts are filled with perilymph -endolymph is produced continuously; it has a special composition and provides a special environment for sensory cells in this organ -b/c its produced continuous, it is drained off, otherwise it would expand/overflow When “unrolled”, the cochlea consists of 3 parallel fluid-filled channels: 1. Vestibular duct 2. Cochlear duct 3. Tympanic duct The organ of Corti sits on the basilar membrane and is partially covered by the tectorial membrane If you’re sitting in total silence, there’s a certain amount of NT being released by the hair cell; sits at a membrane potential at -30 mV When a wave shifts the cilia, they move one way which results in an increase in NT and an increase in frequency of AP; if moved the other way, it will release less (or no) NT and less (or no) Aps Conductive: sound cannot be transmitted through either the external or middle ear -Issue with conduction between tympanic membrane to oval window  infection -Issue with conduction between outer ear to tympanic membrane  ear wax disrupts/blocks transmission Central: results from damage to the neural pathways between the ear and the cerebral cortex or from damage to the cortex itself (ex. strok
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