Wallerian Degeneration & Repair

• Wallerian Degeneration & Repair:

  • the degeneration and regeneration process of a neuron following an injury
  • generally, describes the process following axonotmesis
• Wallerian Degeneration & Repair pt1:

  1. uninjured, normal nerve
  2. initial damage to the nerve and following 24 hours
  3. impulse cant travel from cell body to axon terminal
  4. Schwann cells become disorganised, drop their myelin, release cytokines to signal other cells what to do and release growth factors in preparation for repair
  5. first week following nerve injury
  6. cytokines become active, signalling macrophages start working to clear up debris
  7. growth factors allow the axon to start regrowing from the cell body

  
• Wallerian Degeneration & Repair pt2:

  1. (step 4) following weeks and months
  2. Schwann cells reorganise along the axon
  3. enlargement of cell body and cell nucleus
  4. cell nucleus releases Nissl bodies (type of rough endoplasmic reticulum) which helps with protein synthesis, so helps the axon to grow
  5. axonal growth rate is around 1 mm to 3/4 mm per day
  6. (step 5) weeks/months/years after injury depending on initial injury
  7. repaired neurone
  8. new Schwann cells are slightly smaller than the ones that were not injured, so Nodes of Ranvier are closer together, meaning slower speed of conduction