Types of neurones

• What proportion of peripheral neurones are myelinated?

  About a third
• What is the structure of myelinated nerve fibres?

  • Myelin sheath wraps around the axon
  • Schwann cells embed the myelinated fibres
  • Nucleus and cytoplasm of Schwann cells support and cushion the axon
• How do Schwann cells differ in myelinated and non-myelinated neurones?

  Myelinated neurones have Schwann cells that wrap around the axon, while non-myelinated neurones do not.
• Why do impulses travel faster in myelinated neurones?

  Because of the saltatory conduction that occurs at the Nodes of Ranvier.
• What is saltatory conduction?

  It is the jumping of action potentials between the Nodes of Ranvier in myelinated neurones.
• What role do Schwann cells play in saltatory conduction?

  They provide insulation that allows action potentials to jump between nodes.
• How does the conduction of impulses differ in non-myelinated neurones?

  Impulse conduction occurs across the entire membrane, causing a gradual decrease in the action potential gradient.
• What are the differences in impulse conduction between myelinated and non-myelinated neurones?

  Myelinated neurones:

  • Faster impulse transmission
  • Saltatory conduction at Nodes of Ranvier

  
  

  Non-myelinated neurones:

  • Slower impulse transmission
  • Continuous conduction across the entire membrane
• What happens to the action potential in non-myelinated neurones?

  It moves as a wave and gradually decreases along the neurone.
• What is the effect of the action potential gradient in non-myelinated neurones?

  The gradient decreases gradually along the neurone.