Ear

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How is the vestibular system sensitive to acceleration (linear or rotational)? Explain the mechanism.3 semi-circular canals, rotated 90 degrees towards each other.Each canal is sensitive to acceleration in a different plane.Canals filled with fluidIf it is sensitive to acceleration, then why can the vestibular system also detect the orientation (tilt) of the head?gravityCan the vestibulo-ocular reflex be adapted? Give an example of this and explain where in the brain this adaptation occurs?yes, example slide 16 (vestibulo-ocular system).Adaptation occurs in the cerebellumPosture is suggested to be maintained through the combination of visual, vestibular and somatosensory input. Does the relative contribution of each of these change?yes, i.E. When you are in a dark room, you don’t have much visual information à we need to be able to adapt these depending on the conditions that we are in :small differences/changes à somatosensory input dominates.Bigger differences/changes à more relative input form vestibular systemDescribe the features of the external ear that are relevant for sound localization and the mechanism by which they work.multiple pathways that the sound comes in (some longer, some shorter) à differences in time of arrival à some signals are going to add together, some subtract from each other à results in different frequencies à affects gain. Gain: for a certain input, what is the size of output you get.Notch frequency = where gain is negative (frequencies are out of phase)What is the head-related transfer function (HRTF)? What features of the HRTF allow localization of an object in distance, azimuth and elevation?comparison between one ear and the other.Depends on torso, head position, shadowing of the body,.How our own body and its orientation is going to change the sound à we can use that to detect where the sound comes from.Elevation: notch filer effect.Distance: power of signal (decrease in power as sound distance increases), removal of high frequencies for distant sounds (high frequencies don’t travel well).Azimuth (direction): time difference between the two ears (only for low frequencies)What role does the middle ear play in hearing and why is it necessary?sound = vibrations in air (in outer ear), vibrations in fluid (in inner ear) à we need to transmit sound from motion in air to motion in fluid à role of middle ear.Increase in gain necessary because fluid is harder to move.Two ways to increase gain:1.Mechanical lever 2. Difference in area (area of oval window 21x smaller than area eardrum).Middle ear also protects inner ear from loud noise (through contraction of muscles in middle ear)

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