synapses and reflexes

• • synapses connect two neurones
  • the signal is transferred by chemicals which diffuse over the gap between neurones
  • the chemicals set off an electrical signal in the next neurone
• • reflexes are rapid, automatic responses to stimuli that don't involve the conscious part of the brain
  • reflexes help to prevent injury
  • if a bright light is shined in eyes, pupils will automatically shrink so less light goes into eye
  • the passage of information in a reflex from a receptor to effector is a reflex arc
• reflex arcs:

  • neurones in reflex arc go through spinal cord or unconscious part of brain
  • when stimulus detected by receptors, impulses sent along sensory neurone to relay neurone in CNS
  • impulses reach synapse between sensory and relay neurone, trigger chemicals to be released
  • chemicals cause impulses to sent along relay neurone to motor neurone
  • impulses reach synapse between relay and motor neuron, chemicals released and cause impulses to be sent along motor neurone
  • impulses travel along motor neurone to effector which produces response
• • the response from reflex arcs are quicker than normal responses because they are not thought about