the reflex arc

• there are different types of neurones that work together in a reflex action.

  this creates an automatic and rapid response to a stimulus which minimises any damage to the body like touching something hot.
• what is the sequence of the reflex actions?


  stimulus, receptor, sensory neurone, relay neurone, motor neurone, effector, response
• what is the order of the reflex arc

  1. receptors in the skin detect a stimulus
  2. sensory neurone sends electrical impulses to relay neurone which are located in the spinal cord.
  3. motor neurones sends electrical impulses to an effector
  4. effector produces a response
• what is the gap between two neurones called?

  a synapse
• how does an electrical message/impulse travel across the synapse?

  1. an electrical impulse travels across the first axon
  2. this triggers the nerve ending of a neurone to release chemical messengers called neurotransmitters
  3. these chemicals diffuse across the synapse and bind with receptor molecules on the membranes of the second neurone
  4. the receptor molecules on the second neurone bind only to the specificneurotransmitters released from the first neurone. this stimulates the second neurone to transmit the electrical impulse