14. Number : Rods- 110 to 125 million Cones- 6.3 to 6.8 million Distribution :Rods 0 1,60,000 30,000 Cones 1.47,000 to 5000
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17. Intracellular disk Disk membrane Connecting cilium outer segment outer segment Disk membrane Intracellular space Extracellular space Visual pigment Visual pigment Extracellular space Plasma membrane Intracellular space Connecting cilium ROD CELL CONE CELL PHOTORECEPTORS IN THE EYE
18. VISUAL PIGMENTS : Rhodopsin : Opsin [glycoprotein] & Retinal Two isomeric states of retinal – All trans form --11 cis form Unbleached rhodopsin – reddish purple [due to visual purple] Peak absorption at 500 nm wave length -coresponds to deep green,.. Photopsin : absorption peak at 565 nm blue sensitive - 440 nm green sensitive – 540 nm red sensitive - 570 nm
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20. In Dark :- Depolarisation - Na extruded from inner to outer [-40 mv] segment – open channel In light :- Hyperpolarization – Closure of Na channel [-70 mv]
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22. Photo receptor cell renewal 1-2 Weeks - turnover , Daily 100 discs shed Balance maintained between-shedding and resynthesis of disc membranes. Discs engulfed by RPE into phagosome vesicles then digested by lysosomes and enter bruch membrane,..
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38. They connect laterally between the synaptic bodies of the rods and cones, as well as connecting with the dendrites of the bipolar cells. The outputs of the horizontal cells are always inhibitory. This is called Lateral inhibition .