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VISUAL INFORMATION: Rods: Dim Light: Their rhodopsin is very sensitive to light. A small amount of light can lead to degredation of rhodopsin. (only rods are working in dim lighting) Fuzzy Images (Convergence): Fuzzy images rely on convergence. Gray Tones: Rhodopsin responds to all lights in visual spectrum. That’s why it only sees gray tones. Peripheral Vision: AS we go to the periphery of the retina, our rods increase in density. (there are more rods) That’s why things in periphery are kind of “fuzzy”. Night Vision: Cones: Bright Light: Require a lot of light to break down rhodopsin. Sharp Imagines (Direct Lines): Many have direct lines to visual cortex. Color Vision: Blue/Green/Red/Opsins: Different photoopsins. Same retinal molecule, different opsins associated with that molecule. The different opsins give different light absorbing capacity. High Acuity/Vision: Highest density. Cones increases as we move from periphery from macula. Fovea has a highest accumulation of cones. Macula Horizonal/Amacrine Cells: [look at layers in retina] Enhance Contrast: Because vision is based on contrast. Sharpen Edges Changing Light Conditions Rod and Cones Cross Talk: Horizontal Cells
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Bipolar Neuron Cross talk: Amacrine Cells Muller Cells: Progenerative Cells: Can differentiate into rods and cones if damage to retina Isomerase: Can help resynthesize rhodopsin. Converts all trans. (retinal pigment epithelium and isomerase from muller cells can help resynthesize rhodopsin) Metabolic Barrier: Inner and outer limiting membrane. Inner=basal lamina. Outer=Cell to cell contacts formed by the cells. Prevents large molecules from moving from the choroid into the retina. Questions: A device that monitors the activity of the photoreceptor cells of retina indicates that there is a sudden decrease in the flow of neurotransmitter being released by the photoreceptor cells. This information implies that the subject. Answer: Has moved outside into bright sunlight. (more light, less neurotransmitter) (In the dark, there is more neurotransmitter being produced by the photoreceptor cells because rhodopsin is inactive and cGMP is being produced which leads to the opening of Na channels, depolarization, increase in Ca, and an increase in neurotransmitter by the photoreceptor cell to the bipolar cell) Question 2: A device that monitors the membrane potential of the bipolar neurons of the retina indicates that there is a sudden hyperpolarization of the bipolar neurons. This information implies that the subject. Answer 2:
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This note was uploaded on 02/21/2012 for the course BIO 89515 taught by Professor Janmachart during the Fall '09 term at University of Texas.

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