A Look at Myelin and Myelin-Related Disorders Essay

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A Look at Myelin and Myelin-Related Disorders

Myelin is the protective sheath around axons in the nervous system, and is often referred to as 'white matter.' It acts as an insulator to the electrical signal that is conducted down the axon as a neuron fires, and can well be compared to the insulation around an electrical wire. The myelin sheath contains a variety of fatty substances (lipids), and contains at least ten distinct chemicals (2). . From what is known, axons are not fully myelinated at birth, but myelin is formed from birth on into the second decade of life (3). The way myelination takes place is through glial cells wrapping around the axons in a spiral fashion. The axons are originally embedded in these glial cells, and the
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After patches of myelin are taken off the axon, oligodendrocytes 'repair' the damage, but in the process cause scar tissue (gliotic plaques). These hard plaques then begin to interfere with the flow of electrical impulses that move through the axon (6).. In most cases, the disease is characterized by alternating phases of relapsing and remission, where the remission phases get increasingly shorter. The symptoms include spasticity, double-sightedness (diplopia), and an unsteady gait (5).. This may suggest that it is not the case that myelin in the CNS in general is targeted, but that rather myelin in specific regions is affected. In case of the symptoms above, we might suspect demyelination of some motor neurons, or neurons related to the function of the visual cortex.

The second group of demyelinating diseases,hereditary metabolic disorders, are degenerative diseases and include, among others, the eight identified leukodystrophies (5). Here, 'leuko' means 'white', and refers to the white matter (myelin sheaths) of the central nervous system, and 'dystrophy' means 'imperfect growth or development' (2).. The majority of the leukodystrophies are storage disorders, where the absence or malfunctioning of an enzyme results in the toxic accumulation of chemical substances (5) In each of the so far identified leukodystrophies only one of the
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