Tuesday, February 11, 2014 CC-BY-NC

Maintainer: admin


  • myelin makes action potential go faster
    • saltatory conduction: jumping of action potential from one booster station to the next, 10 times faster than unmyelinated axon
    • Node of Ranvier : Gaps between sections of myelination, booster stations
  • Schwann cells myelinate one single axon
  • Oligodendrocyte can myelinate 50+ axons



  • Major dense line: between layers of myelin, extracellular
  • intraperiod lines: appear like a line, cytosol of myelin, intracellular


  • 70-85% lipids and 13-30% protein
  • no lipid specific to myelin
    • important to maintain formation of myelin sheath
  • major proteins
    • MBP (myelin basic protein) - in CNS and PNS
      • on cytoplasmic face of membrane
      • stabilizes major dense line
      • EAE: autoimmune disease against it
      • shiverer : MBP mutant mouse, shiver a lot.
        • lack of dense lin in CNS,
        • PNS isn't too affected (probably due to Po)
    • PLP (Proteolipid protein) - specific to CNS myelin
      • Transmembrane protein
      • stabilizes intraperiod line of CNS
      • jimpy : PLP mutant mice, tremors and seizures
    • Po (protein zero): specific to PNS
      • immunoglobulin superfamily of cell adhesion molecule
      • promotes formation of intraperiod line (homophilic binding to the adjacent layer)
      • and major dense line (via positively charged cytoplasmic domain)
      • function similar to BMP
  • minor protein
    • MAG (myelin associated glycoprotein)
      • member of Ig superfamily of cell adhesion molecule
      • KO mice: degenerative alterations of PNS myelin
      • mediator of the axon glial adhesion that precedes myelination
      • direct initial tucking under the myelin rings
    • P2
      • stability of the major dense line
    • CNP
    • OMgp

3Node Formation

  • glial cell adhesion molecules are recruited to the point of contact between neurons and glia
  • ankyrin G retamins and stabilizes ion channels at notes of Ranvier
  • paranode and justaparanode act as molecular block and mkae sodium channels and other proteins stay between the noes

4Myelin and nerve regeneration

  • CNS don't regenerate well because their environment is inhibitory
    • removal of debris is also slow and myelin membrane produce molecules that inhibit growth
  • PNS is faster. faster macrophage clearance

4.1Demyelinating Diseases

  • acquired diseases (i.e. multiple sclerosis)
  • hereditary nerodegenerative disorders (i.e. leukodystrophies)