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transduction_blank - IX. Visual System IX.A. Eyes IX.A.1....

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IX. Visual System IX.A. Eyes IX.A.1. Compound Each ommatidia is like a separate retina with many light receptors Compound eye has many ommatidia Each ommatidia sees slightly different view The 3 boxes show what is seen by 3 different ommatidia
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Receptive field looking at olive Receptive field looking at pepperoni The fly’s brain constructs this map which makes sense. IX.A.1. Compound eyes In order to make sense of this confusing view, the fly’s nervous system connects up receptor cells within several ommatidia which are looking at the same part of the visual scene, that is cells with the same receptive fields. Using this method the fly’s brain constructs a congruent map of the world out of the fragmentary map of the ommatidia. The fly’s eye sees a fragmentary map, but the fly’s brain perceives a normal picture. View of three different ommatidia
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IX.A.2. Refracting eyes The cells of the retina are arranged with the photoreceptors on the inside, so that light has to pass all the way through the retina before transduction can occur. .
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IX.B.1. Photoreceptors IX.B.1.a Structure C o l o r B&W vision responds to low light levels
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IX.B.1.b Transduction 1 ______________________________ 2 ______________________________ Light absorbed by rhodopsin 3 ______________________________ 4 ______________________________ Transducin activates phosphodiesterase 5 ______________________________ 1. 2. 3. 4. 5.
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What do you think happens next These Na+ channels close 6 ______________________________ & What does this do? 7 ______________________________ There are Na + channels in the outer segment which are cGMP gated IX.B.1.b Transduction 6 less
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Herman Grid We need to go over a lot of basic stuff, and then we will be able to explain
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IX.B.2. Retinal Circuitry
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_______________ IX.B.2.a. "OFF" and "ON" pathways Off Pathway (signals dark with depolarization) Photoreceptor voltage change Amount of x-mitter released _______________ _______________ On-bipolar cell voltage change _______________ On-ganglion cell firing rate _______________ _______________ _______________ On Pathway (signals light with depolarization) hyperpolarize _______________ _______________ _______________ _______________ _______________
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IX.B.2.b. Lateral inhibition
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The next slide is complicated. If you go to the last one (about 5 forward in your lecture handouts there is a blank version Of the rod-horizontal cell handout. IX.B.2.c Center-surround RFs IX.B.2.b. Lateral inhibition
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Output of pink rod strongly hyperpolarized weakly depolarized weakly hyperpolarized Light 1 Light 2 from horizontal to TO rod = sign-reversing Light 1 only Light 2 only Light 2 from rod to horizontal is sign-preserving Light 1 Light hyperpolarizes black rod Rod to horizontal sign preserving horizontal cell hyperpolarizes
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This note was uploaded on 12/06/2009 for the course NPB 100 taught by Professor Chapman during the Fall '08 term at UC Davis.

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transduction_blank - IX. Visual System IX.A. Eyes IX.A.1....

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