Nervous system

• Nerve cells

  • Are a bundle of neurones such as the sensory, motor and relay neurones
• Receptors


  Detect stimulus and stimulate electrical impulses in response
• Effectors


  Produce a specific response to a detected stimulus, e.g. muscles contracting
• Reflex Arc


  1. Stimulus

  2. Receptor detects stimulus

  3. Sensory neurone sends electrical impulse to relay neurone

  4. Relay neurone relays impulse to motor neurone

  5. Motor neurone sends electrical impulse to effector

  6. Effector produces response
• Central Nervous System


  • Brain
  • Spinal Cord
• Homeostasis


  Maintains optimal conditions for enzyme activity throughout the body
• Sensory neurone


  Sends electrical impulse to relay neurone
• Relay neurone


  Relays impulse to motor neurone
• Motor neurone


  Sends electrical impulse to effector
• Effector


  Produces response
• Homeostasis maintains


  • Blood glucose concentration
  • Body temperature
  • Water levels
• The Brain

  • Hypothalamus regulates temperature and water
  • Medulla controls balance
  • Cerebellum controls light in the pupil
• The Eye

  • Cornea retracts light
  • Retina contains light receptors
  • Optic nerve sends impulses from eye to brain
  • Sclera is the tough white outer layer