What is White matter?
[[File:Human brain right dissected lateral view description.JPG|thumb|A dissected human brain]] The [[central nervous system]] is made of two types of [[Tissue (biological)|tissue]]: '''white matter''' and [[grey matter]]. Grey matter contains [[nerve cell]] bodies, and white matter is made of the [[nerve fibre]]s. When a sample is freshly cut, it usually slightly pink in appearance (for both types). When [[wikt:preserve|preserved]] in [[formaldehyde]], white matter appears to be almost white. White matter consists mostly of [[myelin]]ated [[axon]]s:. Myelin is a [[lipid]] tissue (a fat) with [[capillary|capillaries]]. It helps to keep the electrical in the nerve fibre. This is important for fast and accurate sending of signals. In the [[brain]] white matter is surrounded by grey matter most of the time. In the [[spine]], white matter is outside, and grey matter inside: the myelin sourrounds the nerve cells, and helps the transmission of nerve signals. White matter is used to connect different areas of grey matter. If a section of white matter is damaged, the brain may be able to find a different route to replace the lost connection. The brain contains a third kind of tissue, which appears darker. It is called [[substantia nigra]], a part of the brain that is involved in [[pleasure]] & [[wikt:reward|reward]], [[addiction]] and [[movement]]. {{biology-stub}} [[Category:Anatomy of the nervous system]] [[Category:Animal tissues]]