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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, or gray matter in American English, is a major component of the central nervous system, consisting of neuronal cell bodies, neuropil (dendrites and unmyelinated axons), glial cells (astrocytes and oligodendrocytes), synapses, and capillaries.
Gray ramus communicans; White ramus communicans; The grey and white rami communicantes are responsible for conveying autonomic signals, specifically for the sympathetic nervous system. Their difference in colouration is caused by differences in myelination of the nerve fibres contained within, i.e. there are more myelinated than unmyelinated ...
The gray rami communicantes contain postganglionic nerve fibers of the sympathetic nervous system and are composed of largely unmyelinated neurons. This is in contrast to the white rami communicantes , in which heavily myelinated neurons give the rami their white appearance.
Though statistically there are sex differences in white matter and gray matter percentage, this ratio is directly related to brain size, and some [22] argue these sex differences in gray and white matter percentage are caused by the average size difference between men and women. Others argue that these differences partly remain after ...
The white ramus communicans (pl.: rami communicantes) from Latin ramus (branch) and communicans (communicating) is the preganglionic sympathetic outflow nerve tract from the spinal cord. Each of the thoracic, and the first and second lumbar nerves contribute a white ramus communicans to the adjoining sympathetic ganglion , unlike the gray rami ...
White matter fibre dissection is nowadays considered as a valuable tool to enhance our knowledge about brain connectivity, [5] [9] [10] [1] and has been used to validate tractographic results and vice versa with good consistency between the two techniques, [11] but also for neurosurgical training and neuroanatomical teaching.
The gray matter changes can be observed via both gray matter density and gyrification. That the white matter loss is not nearly as clear as that for gray matter indicates that changes also occur in non-neural tissue, e.g. the vasculature or microglia.