PHGY 209 Lecture 24: CNS, Cognitive, Motor (5)
5 Jan 2017
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Document Summary
Retina reports relative intensity of light to the brain. Retinal ganglion cells have center-surround receptive fields: activated only by a small amount of afferent, small rf. They tell the brain how much light is in middle of rf, in relativity to the sides. Some ganglion cells have inhibitory surround, excitatory center; some have excitatory surround, inhibitory center. Subdivided further into have excitatory surround, inhibitory center. Subdivided further into bright/dark center, dark/bright surround, uniform light. These different donut shapes indicate different preferences of the different ganglion cells. So there are two types of ganglion cells. Ganglion cells compare what"s in the center to what surrounds -- Photoreceptors are sensitive to wavelength (so we see colors) Each cone has a different opsin protein different color! Blue cone, red cone, green cone . but only one kind of rods: grey! The opsin molecule determines the chromatic sensitivity of the photoreceptor. **the output of the retina encodes relative values of brightness & color**
