Summary: From Perception To Consciousness

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• What are the main parts of the eye (involved in perceptions)?

  • The cornea
    
  • The pupil
  • The lens
  • The retina
  • The fovea
  • The macula
  • The blind spot
  • The optic nerves

• What are the functions of rods and cones?

  They sample the image that is projected on the retina by the cornea and lens,
  this information is transported to the visual cortex by the optic nerves

• How does the retina pre-proces rod and cone signals?

  The bipolar-, horizontal- and amacrine cells pre-process the information they receive from the rods and cones. 
  the ganglion cells pass this pre-processed information onto the optic nerves

• Rods and cones are sensitive to different wavelengths, which wavelengths are they sensitive to?

  • Short wavelength cones respond best to blue
    
  • medium wavelength cones respond best to green
  • long wavelength cones respond best to yellow or red
  • cones, are not responsible for processing colour, respond best to green

• How do rods and cones translate light into a neural signal?

  • Rods and cones use a protein called Rhodopsin in rods and Photopsin in cones. (different versions of the same protein)
    
  • Light stimulation of Rhodopsin or Photopsin triggers a chain of events that leads to the closure of Na+ channels in the cell membrane.
  • this causes a hyperpolarisation of the cell, which is sent to the bipolar cells which pass it on to the ganglion cells.

• Explain why different cones are sensitive to different wavelengths of light?

  • Different versions of Rhodopsin (or photopsin) are sensitive to different wavelengths.
  • Humans have 4 types (3 for cones, 1 for rods)
    

• How is it possible that some animals are better or worse at discriminating colours?

  Some animals have more types of rhodopsin or photopsin in their retina, which enables them to discriminate better between colours.
  other animals have less thypes of rhodopsin or photopsin in their retina causing them to be worse at discriminating colours

• What causes colour blindness in humans?

  • Retinal colour blindness is caused by the absence of a specific type of rhodopsin-protein.
    
  • this causes the inability to discriminate between different colours.

• How are the cones and rodes divided over the retina?

  • The cones are mostly present in the fovea, the part of the retina directly behind the pupil. There are almost no rods there.
  • vision, and colour discrimination are optimal in this area
  • rods are mostly present in the rest of the retina, but the highest concentrations are in the areas right next to the fovea, the parafovea. 
    
  • The place where no rods and cones are found is the optic disk or blind spot, this is where the optic nerves come into the eye.

• What is wet or dry macular degeneration?

  • it is a disease of the fovea
  • proteins or fluids come into the retina causing to disturb the form of the fovea
  • this can cause blank spots or distortion in your central vision
  • interrupts the things you intentionally want to look at.