L2 - Reflex Actions

• A reflex action is a rapid, involuntary response to a stimulus

  Properties of a reflex action:

  • Fast
  • Automatic
  • Protective (usually)
• The reflex arc:

  1. The stimulus is received by the receptor
  2. An electrical impulse is sent along the sensory neurone to the spinal cord (coordinator)
  3. The impulse moves across a tiny gap (synapse) to the relay neurone
  4. The relay neurone transmits the signal (via another synapse) to the motor neurone
  5. The motor neurone stimulates the effector (the muscle) to carry out the response = contract
• Stimulus -> Receptor -> Sensory neurone -> Synapse -> Relay neurone -> Synapse -> Motor neurone -> Effector -> Response
• Hairs stand on end to create a thicker layer of insulating air.