brain and eye

• Cerebrum


  • Split into 2 hemispheres
  • Controls intelligence, personality, Conscious
• Cerebellum


  • Controls balance, co-ordination of movement and muscular activity
• Medulla


  • Controls unconscious activities such as heart rate and breathing rate
• Hypothalamus


  • Regulating centre for temperature and water balance within the body
• Cornea


  Refracts light - bends it as it enters the eye
• Iris


  Controls how much light enters the pupil
• Lens


  Further refracts light to focus onto the retina
• Retina


  Contains light receptors
• Optic nerve


  Carries impulses between eye and brain
• Sclera


  Tough white outer layers of the eye that help protect it from injury
• Pupil reflex


  1. Dim light = dilated pupil, radial muscles contract

  2. Bright light = contracted pupil, circular muscles relax
• Reflex action

  1. Receptor in skin detects a stimulus

  2. Sensory neurone sends electric impulse to relay neurore (located near the spinal chord)

  3. Motor neurone sends electrical impulses to an effector

  4. Effector produces a response
• Synapse


  Where two neurones meet
• Transmission across a synapse

  1. An electrical impulse travels along first axon

  2. This triggers the nerve-ending of a neurone to release chemical messengers called neurotransmitters

  3. These chemicals diffuse across synapse and bind w/receptor molecules on the membranes of the second neurone

  4. The receptor molecules on the second neurone bind only to the specific neurotransmitters released from the first neurone

  5. They stimulate the second neurone to transmit the electrical impulse
• short sighted 


  cannot focus on distant objects
• long sighted


  cannot focus on near by objects
• short sighted explanation

  light focused infront of the retina
• long sighted explanation

  light is focused behind the retina instead of onto it
• how can long sightedness be fixed

  by putting a convex lens infront of the eye
• how can short sightedness be fixed

  by placing a concave lens infront of the eye