Mammals have acquired property known as myelin during the evolution so as to enhance the conductivity of the neuronal impulse. Oligodendrocytes produce vast amounts of myelin, a unique and lipid-rich biomembranes with a relatively simple array of myelinspecific proteins in the central nervous system. This membrane, an extension of the oligodendrocyte plasma membrane, forms multilamellar and spirally wrapped sheaths around neuronal axons. The gaps between adjacent myelin sheaths are referred to as nodes of Ranvier, and myelin forms lateral loops there. These myelin loops terminate at the paranode region and engage in the formation of a septate-like adhesive junction with the axon membrane, axolemma. This specialized axo-glial junction acts as an electronical and biochemical barrier between nodal and internodal membrane compartments. Voltagegated sodium channels concentrate in the nodal axolemma, whereas shaker-type K+ channels, Kv1.1 and Kv1.2, localize within the juxtaparanodal axolemma. Saltatory conduction of the action potential is attributed to this organization. The adhesion of myelin to the axolemma plays a critical role in this clustering of ion channels. Thus myelin serves not only as a simple insulator but also as a functional platform of the neuron-glia interaction (Fig. 1).
KeywordsOligodendrocyte Differentiation Myelin Membrane Saltatory Conduction Simple Array Neuronal Impulse
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