PSYC 2390 Lecture : Vision Part 2.docx
1 Aug 2013
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Width of postage stamp: many different types of cells. Rods and cones: back of the retina, all have photopigment in them (in layers) Rhodopsin photopigment for the rods (red) Doesn t absorb red very well (reflects back) Purkinge shift: rod system is night vision system, does not absorb red very well. When exposed to light, pigment becomes transparent. Molecule changes shape and then falls apart when exposed to light. Image that you saw is literally traced on retina, if you get animal right away, can see image on retina. Bleaching causes chemical reaction (enzyme cascade) which results in action potential transduction in vision: 120 million rods, specialty in low illumination vision. Poor visual acuity (problems seeing fine detail) No colour vision (black and white vision) More rods in periphery of vision and farther you get to the periphery, more and more rods. Only 1 million retinal ganglion cells lots of convergence of rods to ganglion cells.
