lecture23sensory

lecture23sensory - LS 2 Sensory Biology NOVEMBER 1, 2010...

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Unformatted text preview: LS 2 Sensory Biology NOVEMBER 1, 2010 Daniel E. Lieberman Office hours: Tue 1-2; and by appt (danlieb@fas.harvard.edu) A major task of the nervous system is to sense environmental stimuli- movement- temperature- color- etc Todays example: feeding Why? Getting and evaluating information on food , predators & prey was a major selective force on many sensory adaptations. Back to an old theme: our lives today are bizarre We have a high probability of becoming overweight, in part because we LOVE foods rich in fat, starch/sugar We spend little time getting, preparing, & eating food We are rarely hungry We have lots of food choice Weinstein, AR & H Sesso. (2006) Exercise and Sport Sciences Reviews 34: 10-15. 20 30 20 50 40 70 60 1960- 1962 1971- 1974 1976- 1980 1988- 1994 1999- 2002 10 Obese Overweight Overweight+ Obese Percent (%) US Adults (>20) who are Overweight and/or Obese 2/3! This relationship to food is very recent Foraging: many millions of years! Farming: last 12,000 years Non-agrarian societies: last few hundred years Yet traces of the the importance of procuring food during our evolutionary past are abundant in our biology, especially in the organs of sense Touch (see also your text) Meissners corpuscles (light touch) Merkles corpuscles (touch) Pacinian corpuscles (vibration, pressure) Ruffini corpuscles (temperature) Afferent fiber MECHANORECEPTORS Meissners corpuscles (pressure) Afferent fiber 10-60 Hz The New Head Hypothesis (origin of vertebrates 525 10 6 years ago ) (Gans and Northcutt, 1983) Filter feeding primitive chordate BUT MOST SENSORY SYSTEMS ARE IN THE HEAD Nose to smell Eyes to see Ears to hear Tongue to taste Early vertebrate predator All derived from neural crest cells! GENERAL PATHWAY FOR SENSORY SYSTEMS Stimulus photons chemicals sound waves pressure Receptor photoreceptor chemoreceptor mechanoreceptor Afferent neuron Receptor potential -> Action potential ( stimulus -> frequency) BRAIN Ascending pathway Brainstem --> thalamus -->cerebral cortex Eyes and Light Frequency (Hz) = wavelengths/second Eyes are mostly outgrowth of forebrain (diencephalon) induced by special group of ectodermal cells (lens placode) The eyeball (basic anatomy) Optic nerve 3-layered capsule Sclera (hard)...
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This note was uploaded on 03/29/2012 for the course LS 2 taught by Professor Andrewa.biewener,petert.ellison,anddaniele.lieberman during the Fall '10 term at Harvard.

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lecture23sensory - LS 2 Sensory Biology NOVEMBER 1, 2010...

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