The Nervous System

• Describe how the nervous system works

  • Receptors are cells which detect stimuli
  • Different receptors detect different stimuli
  • Information converted to an electrical impulse
  • Sent along sensory neurones -> CNS -> motor neurone -> effectors
• What is a stimuli

  Change in the environment
• Give an example of a stimuli

  Receptors in eye detect light
• What is the CNS made up of

  Brain + Spinal cord
• What does the CNS do as the neurones pass through

  Coordinates responses
• What are effectors 


  • Muscle or glands
  • Muscles contract -> cause movement
  • Glands secrete a hormone -> creates a chemical change
• Sum up the nervous system

  • Stimuli -> receptor -> sensory neurones -> relay neurones -> CNS
  • -> motor neurone -> effector -> response
• What does the sensory neurone do

  Carry electrical impulse from receptors to CNS
• What does the relay neurone do

  Carry electrical impulses through CNS
• What does the motor neurone do

  Carry electrical impulse to effectors
• Describe the basic structure of a neurone

  • All have a cell body + nucleus
  • Dendrites + dendrons carry nerve impulses TOWARDS cell body
  • Axon carry them AWAY
• What does the myelin sheath do

  Acts as electrical insulator -> helps impulse travel alone at high speeds
• Describe the sensory neurone

  • 1 long dendron carries impulse from receptor -> cell body
  • Cell body located in middle of neurone
  • One short axon carries nerve impulses from cell body -> CNS
• Describe the relay neurone

  • Many short dendrites -> connected directly to cell body -> carries impulses from sensory to cell body
  • No dendrons
  • Axon carries impulse from cell body -> motor neurone
• Describe the motor neurone

  • Many short dendrites
  • No dendrons
  • One long axon carries nerve impulses from cell body -> effector cells