structure & function

• what is the function of the nervous system?

  enables humans to react to their surroundings and coordinate their behaviour
• how does a stimulus lead to a response being carried out by the body?

  • stimulus converted to electrical impulse by receptors
  • electrical impulses pass along sensory neurone to the central nervous system
  • central nervous system coordinates a response
  • central nervous system sends electrical impulses along the motor neurone to effectors
  • effector carries out response
• sequence of events that describes how the nervous system works

  stimulus -> receptor -> coordinator -> effector -> response
• what is a reflex action?

  rapid, automatic response to certain stimuli that don't involve the conscious part of the brain
• why are reflex actions important?

  protection, they prevent harm to the body
• how does a reflex action occur via a reflex arc?

  • stimulus detected by a receptor
  • receptor generates electrical impulses
  • electrical impulses travel along sensory neurone to the spinal cord
  • at a synapse between sensory neurone and relay neurone, chemicals diffuse across the gap and stimulate new electrical impulses
  • chemicals diffuse across a synapse between relay neurone and motor neurone & stimulate new electrical impulses
  • impulses reach effector, response is carried out e.g. muscles contract