The Nervous System

• the nervous system

  enables humans to react to their surroundings and coordinate their behaviours
• functions of nervous system

  • sensory
  • motor
• name of cells of the nervous system

  nerve cells
• information is passed via electrical impulses
• the nervous system is organised by...

  • receptors
  • neurones
  • CNS
  • effectors
• two parts of CNS

  brain

  spinal cord
• neurones transports electrical impulses around the body
• there are 3 types of neurones

  • sensory
  • relay
  • motor
• effectors are either a muscle or gland
• sensory neurones

  carry impulses from receptors to CNS
• relay neurones

  carry signals from sensory to motor neurones

  found in CNS
• motor neurones

  carry signals from CNS to effectors
• adaptation of nervous system

  • effective communication
  • rapid
  • throughout the body
• a nerve cell is adapted

  • axon - long & thin to carry over long distances
  • carry impulses in one direction - prevent confusion
  • myelin sheath - insulation to prevent impulses being lost
  • dendrites - form connections to cover large areas
• nerve cell

  A) dendrite

  B) cell body

  C) nucleus

  D) axon

  E) myelin sheath

  
• synapses

  gap between neurones
• in a synapse

  • electrical signals travel down axon
  • neurotransmitters are released into the gap
  • neurotransmitters bind to receptor on the next neuron
  • changes in membrane potentially occur
• reflexes are rapid involuntary responses which dont require the brain
• reflexes prevent injury and protects us from danger
• reflex arc response - hot pan

  • receptor picks up stimulus in skin
  • impulse passed onto sensory neurone
  • sensory neurone passes impulses to spinal cord
  • spinal cord/ relay neurone sort out a response & sends message to motor neurone
  • motor neurone tells muscle to contract
  • finger moves away