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Lecture 4

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Matthias Niemeier

Lecture 4– auditory and vestibular system Describe 3 pathways of visual system that are differently specialized for motion, colour, and shape – Magnocellular, Parvocellular, Conocellular Hearing and Balance – based evolutionary (still in fish) called lateral lines system – helpful to sense acceleration – response to differentenents Sound – air molecules that bunch together in regions of lower and higher air pressure – Amplitude – air pressure – Max - Min = intensity – pitch – perception of frequency – amount of physical energy (sound level on graph) – The one ( dot blue) that are at the same horizontal dimension but since the second is on a higher level, it will be perceived as louder – Outer ear – pinna and auditory canal – Tympanic membrane – sound pressure waves – three bones – smallest bone in body – ossicles – oval window – cochlea – Auditory vestibular nerve Function of bones – Since the surface area of the needle is smaller than the surface area of the other end of needle then it goes into the arm of the boy and not into hand of physician even though the pressure is the same The attenuation reflex – we listened to louder, higher sound and ignore lower sounds – High potassium in endolymph is important! Usually potassium goes out and not in – basal membrane images stretched out – the cochlea is wide at the beginning and small at the end but the basal membrane (blue) is narrow at beginning and large at the end and floppy (floppy = lower frequency detection end and higher frequency at beginning) – Stapes causes pressure waves – Frequencies move the basilar membrane – different neurons respond to different frequencies along basilar membrane – Organ of Corti – inner hair cells – touch techtorial membrane – as basilar membrane moves, the organ of corti touches the techtoral membrane TRPAI channels – if brushing towards long one, the distance larger then potassium enters which gives rise to depolarization – Hyperpolarization when leaning away from long hair Afferents – influx of Efferents – amplify the sound by Prestine (motor proteins) which cause cell to change length due to hyperpolarization or depolarization Article – mammano and Ashmore – outer hair cells with amplification – contract or expand – hair cell moves around (twitches) when exposed to sound – especially when putting pipette near outer hair cells, you get mechanical response – opposite effect of RL and BM since both are contracting so both more in opposite directions but one is stronger than the other which is why one is more than the other – Voltage-dependent – the more depolarization more displacement and different on both – triangle of Corti – fulcrum system – outer hair cells pull on Triangle of Corti and the Basiler membrane is pulled up – the sound of that goes in and then if the sound that comes out is different they use this to see if this is a normal ear Central
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