Structure and function

• Function of the nervous system

  allows the body to react to its surroundings and coordinate an appropriate response
• How does a stimulus lead to a response being carried out by the body?

  • stimulus is converted into an electrical impulse by the receptors
  • electrical impulse passes along sensory neurones to the CNS
  • CNS coordinates an appropriate response and an electrical impulse is sent along motor neurones to the effector which carries out the response
• What sequence of events describes how the nervous system works?

  Stimulus -> receptor -> coordinator -> effector -> response
• What is a reflex action?

  automatic and rapid response which doesn’t involve any conscious input from the brain
• Why are reflex actions important?

  aid survival by preventing harm to the body
• Describe how a reflex action occurs via a reflex arc

  • stimulus is detected by a receptor
  • electrical impulses passes along a sensory neurone to the spinal chord
  • at a synapse between a sensory neurone and a relay neurone, a chemical diffuses across the gap and stimulates a new impulse which passes along the relay neurone
  • at the effector, an appropriate response is carried out
• The difference between a reflex pathway and a conscious pathway

  • within a reflex pathway, the coordination centre is a relay neurone found in the spinal cord/unconscious parts of the brain
  • in a conscious pathway, the coordination centre is in the conscious part of the brain