Neurones

• what's DNA

  • polymer made from repeating nucleotide
  • double helix
  • weak hydrogen bonds
  • A + T
  • C + G
  • Sugar phosphate backbone
• describe the general structure of a neurone

  • all have a cell body with nucleus
  • dendrites + dendrites carry nerve impulses TO cell body
  • axons carry impulses AWAY from cell body
  • axons = after the cell body
• what does the myelin sheath do

  • electrical insulator = helps travel at high speeds
• what does a general neurone look like 


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• describe the structure of a motor neurone

  • many short dendrites to carry nerve impulse from CNS -> cell body
  • 1 long axon carries impulse from cell body to effector cells
  • axon made up of muscle fibres
  • NO DENDRONS
• what does a motor neurone look like 


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• describe the structure of a relay neurone

  • NO DENDRONS
  • many short dendrites carry nerve impulses FROM sensory to cell body
  • axon carries nerve impulses from cell body to motor
• describe the structure of a sensory neurone

  • one long dendron carries nerve impulse from receptor cells to cell body
  • 1 short axon carries nerve impulse from cell body to CNS
  • Dendrites receive impulses from receptor cells
• name and explain the roles of the neurones

  • sensory neurone = carry electrical impulse from receptors -> CNS
  • relay = carry electrical impulse through CNS
  • motor = carry electrical impulse to effectors
• what does CNS stand for

  central nervous system
• what does a relay neurone 


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• what does a sensory neurone look like 


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• describe the 1st step of the nervous system

  • stimulus noticed by sensory receptors
  • different receptors detect different stimuli
  • ('eg') eyes detect light/ skin detect pressure (touch)
• describe the 2nd step of the nervous system

  • when stimulus detected by receptors -> info changed to nervous (electrical impulse)
  • sent along sensory neurones to CNS
  • CNS = brain + spinal cord
• describe the 3rd step of nervous system

  • CNS coordinates responses
  • impulses travel through CNS
  • along relay neurones
• describe the 4th step of the nervous system

  • CNS sends electrical impulse to effector along motor neurone
  • effector along MOTOR neurone
  • effectors = muscles or glands
  • so when impulse reaches them muscles will CONTRACT or gland secrete a hormone
  • contract = causes movement
  • hormone = creates chemical change