This presentation covers most of the basic sciences of Retina,...

9. RETINA FOVEA vs

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

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

20. In Dark :- Depolarisation - Na extruded from inner to outer [-40 mv] segment – open channel In light :- Hyperpolarization – Closure of Na channel [-70 mv]

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,..

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 .