Factors affecting conduction

• Speed of conduction of an impulse


  How quickly the impulse is transmitted along a neurone
• Factors that affect the speed of conduction

  • Myelination
  • Diameter of the axon
  • Temperature
• Myelination


  • Whether or not the axon is insulated by a myelin sheath
• Unmyelinated neurones


  Speed of conduction is very slow
• Myelin sheath


  Formed from Schwann cells
• Saltatory conduction


  1. Action potentials 'jump' from one node of Ranvier to the next

  2. Allows the impulse to travel much faster (up to 50 times faster) than in an unmyelinated axon of the same diameter
• Axon diameter


  • Thicker axons have an axon membrane with a greater surface area over which the diffusion of ions can occur
  • Thicker axons possess a greater volume of cytoplasm which reduces their electrical resistance
• Colder temperatures


  Slows down the conduction of nerve impulses
• Mammals maintain very stable body temperatures, so temperature does not usually affect the speed of nerve impulses in these animals
• Cold-blooded reptiles have body temperatures that can vary with the environment