Multiple sclerosis has two essential characteristics: For one, the brain, and partially the spinal cord, are affected by widespread inflammations, because the myelin sheaths are attacked by the body`s own immune defense cells. The consist of a dendrite, a perikaryon, and an axon. Dendrites (gr dendros = tree) receive signals by the preceding nerve cell and are shown in the upper third of the picture. The perikaryon (cell body) is the contact point of the dendrites and the starting point of the axon. It contains the cell organelles and nucleus. The lower half of the picture shows the axon with its branched terminals. It conducts the signal to the next nerve cell. The myelin sheaths are wrapped around the axon, isolating it, and therefore accelerating the conduction velocity. The Ranvier`s nodes are between the myelinated sections.
