Rod cells

• rod cells

  • photoreceptor
  • detect monochromatic light
  • work well in low light conditions
  • outnumber cone cells 3:1
  • has light sensitive pigment - rhodopsin (opsin + retinal)
• Rod cells in light


  • rhodopsin - photosynthetic pigment -> outer segment
  • lights causes it to breakdown
  • into retinal + opsin (rod cell bleached)
  • opsin binds to Na+ channels, blocking them
  • Na+ cannot move into rod cell inner segment
  • Na+ pumped out of inner segment (hyperpolarisation)
  • Glutamate not released at inhibitory synapse
  • Bipolar neurone not inhibited
  • Na+ channels open
  • Depolarising BPN
  • A.P generated to brain via optic nerves
  • So we can see the light

  
• rod cells in dark

  • No light so
  • rhodopsin stays intact
  • Na+ channels stay open
  • Na+ enters outer segment
  • diffuse down conc gradient
  • into inner segment
  • depolarisation
  • glutamate is released into inhibitory synapse
  • Binds on receptors on BPN
  • Preventing depolarisation (inhibitory response)
  • No A.P generated, electrical impulse is not sent on optic nerve
  • No info to brain SOOOO WE CANT SEE ANTHING