BIOL 306 Lecture 20: Biol 306 Final review lecture 20-36
11 Dec 2015
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Why is bat cry loud: spherical spreading loss: 6db drop with doubling of distance, atmospheric attenuation (absorption): tradeoff between range and resolution, attenuation on the way out (pulse) and the way in (echo) Cf (constant frequency)-fm (horseshoe bat and mustached bat)-tuned to a particular frequency (auditory fovea) 1: detect fluttering targets against background (acoustic glints caused by doppler shift): echo stronger when wing move towards the bat (perpendicular) Acoustic glints: periodic modulation of echo caused by insect wing beating, stands out against aperiodic echoes from the background: determine relative speed. Bat will decrease its own cf when echo frequency is increased by doppler shift. Size of frequency change is correlated with speed of prey. (overlap of pulse and echo allows for precise determination of frequency compensation change: combination-selective neurons in auditory cortex. Leech: local touch cause bending 180 degs away from the stimulus. 4 p-type mechanoreceptors- tens of interneurons - 10 excitatory/inhibitory motor neurons- longitudinal muscles.
