rods and cone cells

• rods:

  • can't distinguish different wavelengths of light (black and white)
  • detects light of low intensity (due to spatial summation)
• retinal convergence / spacial summation: many rod cells connect to one bipolar cell
• creating generator potential in rods:

  • pigment of rod cells must be broken down by light energy
  • need to meet threshold
  • can be met in low light intensity as many rod cells are connected to a single bipolar cell (spatial summation)
  • however, brain can not distinguish between separate sources of light that stimulated it due to retinal convergence
  • gives low visual acuity
• cone cell:

  • absorb different wavelengths of light
  • colour images depend on proportion of each cone cell stimulated
• generating action potential in cones:

  • need high enough light intensity to break down pigment
  • only one cone cell connects to a bipolar cell
  • so brain can distinguish between separate sources of light (high visual acuity)
• why do bipolar cells connect to one cone each?

  • temporal summation
  • only responds to high light intensity
  • gives high visual acuity
• fovea: where light is focused

  • recieves highest intensity of light
• distribution of rods and cones:

  • most cone cells are located near fovea (need high light intensity)
  • rods further away (low light intensity)
• photoreceptor: light receptors in the eye e.g. rods and cones