Nervous system

• The Central Nervous System (CNS) coordinates a response.
• A response pathway

  • Stimulus
  • Receptor
  • Sensory neurone
  • CNS
  • Motor neurone
  • Effector
  • Response
• Sensory neurone

  Passes an electrical impulse from a receptor to the CNS.

  • Surrounded by a myelin sheath which insulates it = faster impulse

  
• Motor neurone

  Passes an electrical impulse from the CNS to the effector cell (muscles)

  • Myelin sheath insulates = faster impulse

  
• The connection between 2 neurones is called a synapse.

  • The electrical impulse triggers the release of transmitter chemicals, which diffuse across the synaptic cleft (gap)
  • These chemicals bind to the receptor molecules in the membrane of the next neurone
  • This sets off a new electrical impulse

  
• Reflex actions are faster impulses as they skip the CNS, and are automatic.

  • Stimulus
  • Receptor
  • Sensory neurone
  • Relay neurone
  • Motor neurone
  • Effector
  • Response
• Reflex actions are done automatically as a means of protection.