Perception lesson 2

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Perception lesson 2

  1. 1. Perception lesson 2The optic nerve and the brain
  2. 2. Learning Objectives• To learn about the blind spot• To understand where visual information is used in the brain
  3. 3. The blind spot• We use the phrase ‘the blind spot’ to mean all sorts of things• I often say I have a blind spot for maths, because I cant see how it works• Drivers use their mirrors to see what is behind them, but there is always a blind spot that the mirrors don’t cover• In your eyeballs there is a small area with no rods or cones, so it is called the blind spot
  4. 4. Why do we have a blind spot• Each rod or cone connects to a neurone (a nerve cell), and these leave the eyeball via the optic nerve (the eyeball stalk)• At the point where the optic nerve leaves the retina there are no rods or cones, so nothing can be detected• This is your blind spot
  5. 5. Blind Spot• demonstration
  6. 6. Blind Spot• You may wonder why you don’t see a hole in your vision.• This is because the two blind spots don’t overlap, so if you cant see a small area with one eye, you can see it with the other• They ‘fill in’ for each other
  7. 7. The Optic Chiasma• From the back of the eyeball the optic nerve travels to the back of the brain• About half way back the two optic nerves (one from each eye) cross over at the optic chiasma• At the chiasma, fibres from each eye swap to the other side• This means that information from each eye goes to both sides of the brain
  8. 8. The optic chiasma
  9. 9. The Visual cortex• The part of the brain that receives and processes information from the eyes is the visual cortex• It is right at the back about half way up (look at the model of the brain)• The visual cortex uses the information from the rods and cones to understand shapes and distances
  10. 10. The visual cortex

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