Section through spinal chord with central grey matter and surrounding white matter. Source: University of Michigan The white matter, again, is formed by various tracts (Fig. 4) and the grey matter with parts that are processing information (fig. 5). read more
• In the Spinal cord, matter is around the outside of the Spinal Cord -- This is the myelinated Neurons surrounding the outside. • In the Brain, the Matter is towards the inside • Matter also includes Nerves of the Peripheral Nervous System (PNS) and all tracts in CNS. read more
Much of the white matter in the spinal cord is arranged somatotopically and serves to get messages in and out of the spinal cord grey matter as quickly as possible (one would suppose). You could think of there being some relay stations in the grey matter, modulating messages from the limbs and trunk on their way to the brain, and in the opposite direction for motor signals from the brain to limb and trunk muscles. read more