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White matter is the tissue through which messages pass between different areas of grey matter within the central nervous system. The white matter is white because of the fatty substance (myelin) that surrounds the nerve fibers (axons). This myelin is found in almost all long nerve fibers, and acts as an electrical insulation.
Grey matter is distinguished from white matter in that it contains numerous cell bodies and relatively few myelinated axons, while white matter contains relatively few cell bodies and is composed chiefly of long-range myelinated axons. [1] The colour difference arises mainly from the whiteness of myelin. In living tissue, grey matter actually ...
Tangential growth suggests that the grey matter grows at a faster rate than the inner white matter and that the growth rate of the grey matter determines the growth rate of the white matter. Though both methods are differential, with the cortex growing more rapidly than the subcortex, tangential growth has been suggested as a more plausible model.
The anterior and posterior grey columns present as projections of grey matter and are also known as the horns of the spinal cord. The white matter is located outside of the grey matter and consists almost totally of myelinated motor and sensory axons. Columns of white matter known as funiculi carry information either up or down the spinal cord.
Each cerebral hemisphere has an outer layer of cerebral cortex which is of grey matter and in the interior of the cerebral hemispheres is an inner layer or core of white matter known as the centrum semiovale. [3] The interior portion of the hemispheres of the cerebrum includes the lateral ventricles, the basal ganglia, and the white matter. [4]
Structure of a typical neuron in the peripheral nervous system A dissected human brain, showing grey matter and white matter. Axons are the primary transmission lines of the nervous system, and as bundles they form nerves in the peripheral nervous system, or nerve tracts in the central nervous system (CNS). Some axons can extend up to one meter ...
The tegmentum area includes various different structures, such as the rostral end of the reticular formation, several nuclei controlling eye movements, the periaqueductal gray matter, the red nucleus, the substantia nigra, and the ventral tegmental area. [3] The tegmentum is the location of several cranial nerve nuclei. The nuclei of CN III and ...
The brain is very complex, and is composed of many different areas and types of tissue, or matter. The different functions of different tissues in the brain may be more or less susceptible to age-induced changes. [6] The brain matter can be broadly classified as either grey matter, or white matter.