NS:response to stim

• 1. stimulus is detected by receptor cells
  2. impulses sent along sensory-relay-motor neurones
  3. impulse recieved by effector
• pupil response

  • changing diametre of pupil helps to control how much light is hitting the retina
  • circular muscles contract to constrict pupil
  • radian muscles contract to dialate pupil

  these muscles work antagonisitically, when one is contracting the other is relaxing
• in bright light

  • bright light detected by light receptors in eyes
  • electrical impulse passed along senory neurone to the CNS
  • CNS coordinates response and send impulse along motor neurone
  • =circular muscles contract and radial muscles relax in the iris-pupil constricts, limiting damage to the retina
• in low light

  • low light detected by light receptors in eyes
  • electrical impulse passed along the sensory neurone to the CNS
  • CNS coordinates response and sends impulse along the motor neurone
  • =circular muscles relax and radial muscles contract in the iris-pupil dilates, allowing more light to hit the retina
• light receptors=photoreceptors