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Exploring the Intricacies of the Retina: From Photoreceptors to Visual Perception

Dive into the complexities of the retina, from the diverse photoreceptor cells to the intriguing visual processing mechanisms. Learn about the distribution of rods and cones, the significance of retinal ganglion cells, the unique properties of the fovea, and the fascinating trichromatic theory of color vision. Discover how light triggers a cascade of events in photoreceptor cells and the importance of parallel processing in the visual cortex. Delve into the groundbreaking experiments by Hubel and Wiesel and explore the intricate pathways in the visual system. Uncover the reasons behind the emphasis on understanding the visual system and its role in our perception of the world.

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Exploring the Intricacies of the Retina: From Photoreceptors to Visual Perception

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  1. The Visual SystemPart 2

  2. The Retina

  3. S 15 More membrane =more photosensitive molecules =more sensitive to light Photoreceptor cells4 light sensitive proteins:rods with 1 type3 types of cones, each with a single type Receptors for light detection Receptor cells

  4. StargazingFinding your car in a dark parking lotChoosing socks

  5. Visual Acuity • 120,000,000 rods and 6,000,000 cones per retina • 1,200,000 retinal ganglion cells & axons • 105:1 convergence ratio • Fovea: cones only, 1:1 highest visual acuity but poor sensitivity Counting fingers andReading the Writing on the Wall

  6. Demonstrationof Blind Spot (diagram)

  7. Differences in spectral sensitivity due to 4 types of opsin. Rods have 1 type; Each type of cone has another type. “Green” cones “Blue” cones “Red” cones Web-based color deficiency test Trichromatic Theory of Color Vision

  8. “Bleaching” of photopigments

  9. The cascade of events initiated by light in a photoreceptor. The result of the cascade is to close a cGMP-gated sodium channel, reducing the inward current and hyperpolarizing the membrane. Source: Kandel, Schwartz & Jessell, Principles of Neural Science, 4th Edn What is the advantage of this multistep process?

  10. Hubel and Weisel Experiments VisualCortexNeurons LateralGeniculateNeurons Youtube RetinalGanglionCells

  11. Parallel Processing in the Cortex • Motion sensitive • Color and shape sensitive Story of woman atstreet crossing

  12. Why so much emphasis on the Visual System?

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