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• • • • • When dark, ROD turned on à ON CENTER bipolar cells inactive, OFF CENTER bipolar cells active. When OFF CENTER bipolar cells turned on, this activates OFF CENTER retinal ganglion cell, which sends signal to optic nerve to brain. Photopic vision occurs at levels of high light levels. Meso...

• • • • • When dark, ROD turned on à ON CENTER bipolar cells inactive, OFF CENTER bipolar cells active. When OFF CENTER bipolar cells turned on, this activates OFF CENTER retinal ganglion cell, which sends signal to optic nerve to brain. Photopic vision occurs at levels of high light levels. Mesopic vision occurs at dawn or dusk and involves both rods and cones. Scotopic vision occurs at levels of very low light. Photoreceptors (Rods and Cones) • • • • • • A photoreceptor is a specialized nerve that can take light and convert to neural impulse. Inside rods are optic discs, which are large membrane bound structures – thousands of them. In membrane of each optic disc are proteins that fire APs to the brain. Cones are also specialized nerves with same internal structure as rod. Rods contain rhodopsin; cones have similar protein photopsin. If light hits a rhodopsin, will trigger the phototransduction cascade. Same process happens in a cone. Differences between rods and cones: 23