brain and eye

• the retina is the light sensitive layer at the back of the eyeball
• the lens focuses light onto the retina
• the optic nerve carries impulses from the retina to the brain
• Receptor cells


  Cells that detect changes in your environment
• Effector

  Part of your body that responds to change (muscle/gland)
• Relay neurons

  1. Found in the central nervous system

  2. Impulses move from dendrites to axon
• Axons

  Lots of short cells body. Nerve impulses
• Nerve impulses

  From all over the body to the central nervous system
• Dendrites

  Short, branching nerve fibers
• Sensory neurons

  Carry impulses from receptor cells to the central nervous system
• Neuron

  • Cell body
  • Nucleus
  • Myelin sheath
• Sensory neuron

  Carries impulse from receptor to central nervous system
• Brain

  Spinal cord
• Motor neuron

  Carries impulse from central nervous system to effector
• Sensory neuron

  Carries impulse to spinal cord
• Pain receptors

  In the skin
• Motor neuron


  Carries impulse from spinal cord to muscle
• Electrical impulse

  • Can't pass through the gap
• Vision

  1. Light from object enters eye

  2. Refracted by cornea

  3. Passes through pupil

  4. Focused by lens

  5. Hits retina

  6. Photoreceptors stimulated

  7. Electrical impulses travel to brain

  8. Brain processes upside-down image
• Photoreceptors

  • Rods and cones
• Pupil dilates

  Radial muscles of iris contract
• Pupil constricts

  Circular muscles of iris contract
• Near vision

  Ciliary muscles contract, suspensory ligaments relax, lens becomes more curved
• Distant vision

  Ciliary muscles relax, suspensory ligaments taut, lens becomes less curved
• Short-sightedness

  Light focuses short of retina, eyeball elongated or lens too strong, corrected by concave lens
• Long-sightedness

  Light focuses long of retina, eyeball short or lens too weak, corrected by convex lens
• Brain


  • Hypothalamus
  • Cerebrum
  • Cerebellum
  • Medulla oblongata
• Damage to central nervous system

  Paralysis of limbs, motor dysfunction
• Damage to peripheral nervous system

  Loss of sensation, burning sensation
• cerebrum- controls intelligence, personality, conscious thought, memory, language
• medulla controls unconscious activities like heart rate and breathing rate
• hypothalamus- regulating centre for temperature and water balance
• Lens: A transparent structure that refracts light and focuses it on the retina.

  
• Cerebrum: controls voluntary movement, intelligence, memory, language, and consciousness

  
• Cornea: The clear outer layer of the eyeball that allows light to enter.
• Iris: The colored part of the eye that regulates the amount of light entering through the pupil.
• Retina: The inner lining of the back of the eye that contains photoreceptor cells responsible for vision.
• Relay neurone: To transfer a signal from a sensory neurone to a motor neurone.
• If too much light reaches the retina, it could get damaged.

  If too little light reaches the retina, we won't be able to see clearly.