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Vision Part 2.docx

19 Pages

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PSYC 2390
Lana Trick

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The Retina 9242012 75800 AM The RetinaDescription and FunctionBack layer of the eyeWidth of postage stamp o Many different types of cellsWhere image is projected onPhotoreceptorsRods and cones o Back of the retina o All have photopigment in them in layersRhodopsinphotopigment for the rods redDoesnt absorb red very well reflects backPurkinge shift rod system is night vision system does not absorb red very wellPigment bleachinglightBleach retinaopsinWhen exposed to light pigment becomes transparentMolecule changes shape and then falls apart when exposed to lightPhotopigment literally changes colourImage that you saw is literally traced on retina if you get animal right away can see image on retinaBleaching causes chemical reaction enzyme cascade which results in action potentialtransduction in vision o 120 million rods specialty in low illumination visionmore sensitive than cone visionpoor visual acuity problems seeing fine detailno colour vision black and white visionmore rods in periphery of vision and farther you get to the periphery more and more rods periphery of vision is less colouronly 1 million retinal ganglion cellslots of convergence of rods to ganglion cells120 rods1 ganglion celladding up signal o cones have 3 different kinds of photopigments only type of cells in foveahave direct line to the brain via retinal ganglia cells ganglion cellsbrain6 million conesfine detail visioncolour vision as you get closer to edge of visual field less and less conesCollector CellsTake information from rods and cones and send information to ganglion cells which send information to eye via optic nerveAxons leave back of the eye at the optic nerve bundle of axons o Part of the eye that does not have any rods and cones o Called the blind spot o Normally what falls in blind spot in one eye is in normal visual field of other eye fills in missing informationPigment EpitheliumHelps recycle photopigments after bleaching enzymes in pigment epithelium o Vitamin A helps bring photopigments back togetherDisordersProblems of the Retina Detached RetinaNormally cause by traumatic injuryCannot register image very well often times would be blurryDiabetic retinopathyEither born with diabetes or develop diabetes agerelated insulin resistant diabetesHave poor circulation in the eye
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