Reflex arc

• What triggers the reflex arc?

  The stimulus, which is heat
• How does the sensory neurone transmit the impulse?

  Via the spinal cord, across a synapse
• What does the receptor do in the reflex arc?

  It sends out an electrical impulse
• What is the role of the relay neurone in the reflex arc?

  It receives the impulse from the sensory neurone
• What happens to the electrical impulse after the relay neurone?

  It travels to the motor neurone
• What do the muscles do in the reflex arc?

  They contract as effectors
• What are the characteristics of reflex actions?

  • Automatic, do not involve the brain
  • Protect from danger
  • Very quick
  • Use three neurones
• Can you name four examples of reflex actions?

  Sneeze, blink, cough, knee jerk
• What are the main components of a neurone?

  • Nucleus
  • Dendrites
  • Cell body
  • Axon terminals
  • Axon
  • Schwann cell
  • Myelin sheath
• What is the function of the myelin sheath in a neurone?

  It insulates the axon to speed up impulses
• What is the direction of impulse in a neurone?

  From dendrites to axon terminals
• What role do dendrites play in a neurone?

  They receive signals from other neurones
• What is the role of the axon in a neurone?

  It transmits impulses away from the cell body
• What is the function of Schwann cells in the nervous system?

  They produce the myelin sheath around axons