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Eye and Retina (Retinal Processing and Output (Ganglion Cell Receptive…

- - - - On
        cones and rods
        
        metabotropic (G-protein coupled)
        
        hyperpolarized by glutamate
        
        depolarized by light
        
        stimulated if light hitting center
      - Off
        just cones
        
        hyperpolarized by light
        
        ionotropic glutamate receptors
        
        depolarized by glutamate
        
        depolarized in dark light in center
    - - horizontal cells counteract effect of photoreceptor
  - - - created by vertical connections
      - much more sensitive than surround
    - - created by horizontal cells
  - - - large RF
      - large objects & movement
      - M (magnocellular) layer of LGN
    - - wavelenghts of light
      - P (parvocellular) layers of LGN
      - small RF
    - - small RF
      - selective to blue center & yellow OFF surround
      - terminate in K (koniocellular) layer of LGN
- - - - center of retina
      - central fovea lacks blue cones & rods
      - packed with cones
    - - "blind spot" bc no receptors
      - here the axons of ganglion cells leave and enter optic disk
    - - Photoreceptors
        
        cones
        
        5 million
        
        photopic (daytime)
        
        3 types
        
        short (blue)
        
        medium (green)
        
        long (red)
        
        found primarily in central retina
        
        #
        
        rods
        
        92 million
        
        1000x more sensitive to light
        
        scotopic (nighttime)
      - Ganglion cells
        
        prefer spot of light
      - Bipolar cells
      - Horizontal cells
      - Amacrine cells
  - - - Transduction of image by photoreceptors
        (photons --> electrochemical energy)
      - Photoreceptors synapse on bipolar cells
      - Synapse on ganglion cells
      - Ganglion axons exit through optic nerve to brain
    - - amacrine and horizontal cells inhibit signals