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Retinal Processing and Output - Coggle Diagram

- - - - ON
        
        “turned on” by light
        
        depolarize
        
        GPCR(metabotropic) receptors
        
        Glu -> hyperpolarization
      - OFF
        
        light (hyperpolarizat. of cone) effectively turns them off
        
        hyperpolarize
        
        have ionotropic glutamate receptors
        
        Glu -> depolarization
      - based on the response to the glutamate released by photoreceptors
    - - response of a bipolar cell’s MP to light in the receptive field center is opposite to that of light in the surround
        
        measured in millimeters across the retina or, more commonly, in degrees of visual angle
    - - also ON and OFF
        
        difference: fire APs :zap:
        
        also: response to stimulation of the center is canceled by the response to stimulation of the surround
        
        rather, mainly responsive to differences in contrast
        
        can be further categorized
        
        two major types
        
        large M-type ganglion cells and smaller P-type ganglion cells
        
        ~ 90% of ganglion cells: P cells, ~5% M, 5% nonM–nonP (less well characterized)
        
        visual response differs
        
        M cells respond to stimulation of their receptive field centers with a transient burst of action potentials
        
        2 more items...
      - overall ganglion cell population sends information to the brain about three different spatial comparisons
        
        light versus dark, red versus green, & blue versus yellow
        
        one special type: ipRGCs
        
        intrinsically photosensitive retinal ganglion cells
        
        blind people unconsciously synchronize their behavior to daily changes in sunlight.
        
        use melanopsin as a photopigment
        
        unlike hyperpolarization to light in rods and cones, ipRGCs depolarize to light
        
        very large dendritic fields (dendrites photosensitive): sum light input over much larger areas of the retina than rods and cones
        
        not used in fine pattern vision, provide input to subcortical visual areas that synchronize circadian rhythms