Lecture-19-2011-Bi-CNS150

Lecture-19-2011-Bi-CNS150 - HAL wont have office hours this...

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1 Bi 150 Lecture 19 Monday, November 14, 2011 Olfaction Henry Lester Reading: Kandel Chapter 32, pp 625-636 (not taste) (What is olfaction?) HAL won’t have “office” hours this Friday, 11/18 http://www.its.caltech.edu/~lester/Bi-150/Lecture-15-2011-Bi-CNS150.ppt
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Bi150 revised syllabus? http://www.amazon.com/s/ref=nb_ss_gw?url=search- alias%3Daps&field-keywords=proust+neuroscientist
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3 What did Proust actually write? “as soon as I had recognized the taste of the piece of madeleine soaked in her decoction of lime-blossom which my aunt used to give me (although I did not yet know and must long postpone the discovery of why this memory made me so happy) immediately the old grey house upon the street, where her room was, rose up like a stage set to attach itself to the little pavilion opening on to the garden which had been built out behind it for my parents (the isolated segment which until that moment had been all that I could see); and with the house the town, from morning to night and in all weathers, the Square where I used to be sent before lunch, the streets along which I used to run errands, the country roads we took when the weather was fine . . . Remembrance of Things Past
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4 Olfactory memory The nose can detect and (in principle) classify thousands of different compounds. The ‘mapping’ of these compounds probably occurs by matching to memory templates stored in the brain; thus, a smell is categorized based on one’s previous experiences of it and on the other sensory stimuli that correlate with its appearance.
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5 Recognition of chemicals by the olfactory system The nose can distinguish very similar compounds as different smells. An example: the two stereoisomers of carvone smell like spearmint and caraway . This implies that there are stereoisomer-specific carvone receptors. Carvone Stereo center
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6 A genetic model system: nematode olfaction C. elegans can chemotax toward and away from volatile attractants and repellents. It uses only two pairs of neurons, AWA and AWC, to respond to volatile attractants. It has many olfactory receptors, however, so each chemosensory neuron must express many of these. The ODR-10 receptor is expressed in AWA and localized to its dendrite. ODR-10 is a receptor for the odorant diacetyl (2,3 butanedione). Worms lacking ODR-10 are not attracted to diacetyl. Figure 32-11 Cell body of AWA neuron Dendrite Cilia Axon
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7 ODR-10 phenotype ODR-10 is specific for diacetyl and does not respond to 2,3-pentanedione, which differs by only one methylene group. ODR-10 mutants still chemotax to 2,3-pentanedione The AWC cell has receptors for 2,3-pentanedione Deletion of AWC destroys chemotaxis to 2,3-pentanedione
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8 ODR-10 recognizes components of a metabolic pathway What is the selective advantage of a worm’s response to diacetyl? Diacetyl results from respiration by certain bacteria.
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Lecture-19-2011-Bi-CNS150 - HAL wont have office hours this...

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