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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.
It is the largest white matter structure in the human brain, about 10 cm (3.9 in) in length and consisting of 200–300 million axonal projections. [2] [3] A number of separate nerve tracts, classed as subregions of the corpus callosum, connect different parts of the hemispheres.
The human brain is the central organ of the nervous system, and with the spinal cord, comprises the central nervous system. It consists of the cerebrum, the brainstem and the cerebellum. The brain controls most of the activities of the body, processing, integrating, and coordinating the information it receives from the sensory nervous system ...
The commissural fibers or transverse fibers are axons that connect the two hemispheres of the brain. Huge numbers of commissural fibers make up the commissural tracts in the brain, the largest of which is the corpus callosum .
The brain can thus be described as being divided into left and right cerebral hemispheres. Each of these hemispheres has an outer layer of grey matter, the cerebral cortex, that is supported by an inner layer of white matter. In eutherian (placental) mammals, the hemispheres are linked by the corpus callosum, a very large bundle of nerve fibers.
The internal capsule is a paired white matter structure, as a two-way tract, carrying ascending and descending fibers, to and from the cerebral cortex. The internal capsule is situated in the inferomedial part of each cerebral hemisphere of the brain. It carries information past the subcortical basal ganglia.
The corpora quadrigemina are reflex centers involving vision and hearing. It consists of groups of nerve cells-grey matter scattered in white matter. It basically connects the forebrain and the hind brain. It has four corpora quadrigemina which are the reflex centres of eye movement and auditory responses.
The arbor vitae / ˌ ɑːr b ɔːr ˈ v aɪ t iː / (Latin for "tree of life") is the cerebellar white matter, so called for its branched, tree-like appearance.In some ways it more resembles a fern and is present in both cerebellar hemispheres. [1]