Neurons

• Cell body


  • Dendrites
  • Axon
• Sensory neurons


  • Carry electrical impulses towards the brain
  • Found in the PNS
• Sensory neurons


  • Have long dendrites
  • Have short axon
• Relay neurons


  • Have cell body
  • Carry signals
  • Allow sensory and motor neurons to communicate
• Relay neurons are only found in the brain/visual system/spinal cord
• Relay neurons


  • Have short dendrites
  • Have short axons
  • Do not have a myelin sheath
• Motor neurons


  Carry Motor commands FROM the CNS to EFFECTORS (skeletal muscles/organs/gland) which allows for movement
• Motor neurons


  • Have short dendrites and long axons (for sending messages)
  • Cell bodies are in the CNS
  • Have long axons that also connect to the PNS
• sensory, relay and motor neurons work together
• For example, if someone picks up a hot pan and then drops it
• SENSORY receptors in the fingers sense the heat and send that information via the peripheral nervous system to the CNS
• RELAY


  neurons would be involved in analysing the sensation of heat and pain, and are involved in the decision to let go - passing messages to the
• MOTOR

  neurons which instruct the effectors to let go of the hot pan