Myelin Sheath Components

The myelin sheath is an insulating layer of fatty tissue that protects the neurons of the body from electrical activity. The myelin sheath helps conduct nerve signals along the neuron. Degeneration of the myelin sheath can lead to disruption in signal conduction. This disruption can lead to symptoms like arm and leg pain, visual changes, impairment in muscle function and difficulty with fine motor control.

Purpose and Presence

• According to the Medline Plus website, the main purpose of the myelin sheath is to allow rapid and efficient transmission of impulses along nerve cells. Myelin covers the central nervous system, including the brain and spinal cord, and peripheral nervous system. Myelin does not usually cover the autonomic nervous system and is not present in invertebrates, according to the Athabasca University website.

Myelin of the Central Nervous System

• The myelin sheath of the central nervous system contains approximately 40 percent water. The lipids constitute about 70 to 85 percent. The major lipids present in the myelin sheath are cerebroside, cholesterol, lecithin and ethanol-containing plasmalogens. A minor lipid component in the myelin sheath is sphingomyelin. Proteins make up about 15 to 30 percent of the composition of the myelin sheath. The major protein components of the central nervous system myelin sheath are myelin basic protein and proteolipid protein.

Myelin of the Peripheral Nervous System

• The myelin sheath of the peripheral nervous system contains the same percentages of water, lipids and proteins. The lipids of the myelin sheath in the peripheral nervous sytem are similar in type to those found in the central nervous sytem, but in different ratios. The major component of protein in the myelin sheath of the peripheral system is P zero, which accounts for about 50 percent of the protein composition. Other protein components are myelin basic protein and P two.

Conditions of Demyelination

• Diseases involving demyelination of the central nervous system include multiple sclerosis, leukodystrophies, optic neuritis and transverse myelitis. Conditions of demyelination of the peripheral nervous system include Guillian-Barre syndrome, Charcot-Marie-Tooth disease and peripheral neuropthy. If you suspect symptoms of any of these demyelinating conditions, contact your health-care provider for appropriate treatment options.