the brain and the eye

• steps on a voluntary action

  1. receptors detect stimuli
  2. sensory neurone
  3. central nervous system
  4. motor neurone
  5. effector
• synapses are gaps between neurones where electrical impulses are converted to chemicals called neurotransmitters that diffuse across
• the brain

  • medulla - involuntary actions like breathing
  • cereberal cortex - memory and language
  • cerebellum - mobility and coordination
• how do scientists study the brain

  • electric stimulation
  • mri scans
  • researching people with brain damage
• retinas have receptors that are sensetive to light and colour these are known as rod and cone cells
• the sclera is a thick hard outer layer
• Cornea: This is a transparent layer found at the front of the eye, used to reflect and bend light into the eye
• optical nerve sends message to the brain
• myeopia is short sitedness
• hyperopia is longsitedness
• in bright light

  • circular muscles contract
  • radial muscles relax
  • pupils consrict
• when looking close

  1. lens thicken
  2. ciliary muscles contract
  3. suspensory ligaments relax
• myeopia

  • light is focused in front of the retina
  • lens is too curved or you have a long eyeball
  • to fix this you need thicker concave lenses
• hyperopia

  • light is focused behind the retina
  • the lens is too flat or you have a short eyeball
  • you need thin convex lens
• during an involuntary action or reflex action the brain is skipped to save time
• iris controls the size of the pupil with suspensory ligaments and ciliary muscles
• treatment

  • contact lens
  • laser eye surgery
  • replacement lenses