-Paul,+Jones.

1. The CNS is full of nerve cells called neurons. These are the brain cells of popular usage. 2. There are different types of neuron in different areas of the CNS. 3. Those in the white matter tissue are the ones most liable to be attacked in multiple sclerosis. 4. This type of neuron is a long thin cell which has a bulbous head (the soma) containing the cell nucleus and an elongated strand called an axon. 5. The soma has thin, branched tendrils called dendrites growing out of it. 6. The axon of one neuron joins to the dendrites of other neurons via a special connection called a synapse. 7. Signals or nerve impulses travel down the axon where they are transmitted to other neurons via chemical signals (neurotransmitters) moving across the synapse. 8. The axon itself is coated with a sheath of insulating fatty protein called myelin which aids the transmission of nerve impulses. 9. A good analogy of the myelin's relation to the axon is the plastic or rubber insulation around electric wires. 10. Oligodendrocytes are the axon's maintenance cells. 11. Their job is to create and repair the myelin sheath and to feed essential factors to the axon. 12. Each oligodendrocye maintains several axons and each axon is maintained by several oligodendrocyes. 13. Oligodendrocyes belong to a larger grouping of maintenance cells called glial cells. 14. Their importance has recently become better understood and, as more and more is discovered about MS, the more central oligodendrocytes, or more accurately their death, has become. In some ways, it is fair to say that multiple sclerosis is a disease of oligodendrocytes. 15. During periods of multiple sclerosis activity, white blood cells (leukocytes) are drawn to regions of the white matter. 16. These initiate and take part in what is known as the inflammatory response. 17. The resulting inflammation is similar to what happens in your skin when you get a pimple. 18. During the inflammation, the myelin gets stripped from the axons in a process known as demyelination. 19. The effect of this bears many parallels to the rubber insulation on wire perishing - some or all of the electricity in the wire will short out and the efficient conductivity of the wire will be reduced. 20. When the myelin sheath is damaged, the transmission of nerve impulses is slowed, stopped or can jump across into other demyelinated axons. 21. Additionally, the inflammation can also damage the underlying axonal membrane. 22. This membrane is a sophisticated structure that enables the nerve transmission (the action potential) to travel along the nerve. 23. It seems that the inflammation also kills the mainenance glial cells, in particular it seems to kill the myelin-producing oligodendrocytes, which are lost in great numbers. 24. Almost no oligodendrocytes persist in the middle of chronic MS lesions **. **25** . **As the disease progresses, axons are also destroyed though not necessarily by the inflammatory response. 26. During the secondary progressive phase of the disease, inflammation becomes less and less common but still the axons continue to die. This degeneration of axons is known as Wallerian Degeneration.
 * Facts: **

Paul, Jones. "All About Multiple Sclerosis." Health On the Net Foundation, 31 Jan. 2008. Web. 17 Sep. 2010. .