Grey matter

Grey matter describes types of tissue in the central nervous system which appear to be a light grey in color. It consists of the central cell bodies of neurons, dendrites, axons, glial cells, and blood capilliaries. It contains more cell bodies than white matter and fewer axons that are not coated by myelin. It's found throughout the different parts of the brain, and forms a roughly H-shaped column through the spinal cord.
The regions of the central nervous system that control muscles and sensory perception are made up primarily of grey matter.
Lower volumes of grey matter have been linked to issues with short term memory and bipolar disorder, among other conditions. In addition, smoking has been linked to lower grey matter volumes.
Grey matter at Wikipedia
Category:Neurology