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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.
Diagram illustrating the theorized causes of NAA accumulation in spongy degeneration patients and its consequences . Although the pathophysiological causes of CD symptoms are still unclear, there are developing theories on the causes of myelination issues, gelatinous cortical white matter and seizures. [8]
Being rich in lipid, myelin appears white, hence the name given to the "white matter" of the CNS. Both CNS white matter tracts (e.g. the optic nerve, corticospinal tract and corpus callosum) and PNS nerves (e.g. the sciatic nerve and the auditory nerve, which also appear white) each comprise thousands to millions of axons, largely aligned in ...
Myelin is formed by oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system.Therefore, the first stage of myelinogenesis is often defined as the differentiation of oligodendrocyte progenitor cells (OPCs) or Schwann cell progenitors into their mature counterparts, [4] followed by myelin formation around axons.
Diffusion tensor imaging (DTI) is important when a tissue—such as the neural axons of white matter in the brain or muscle fibers in the heart—has an internal fibrous structure analogous to the anisotropy of some crystals. Water will then diffuse more rapidly in the direction aligned with the internal structure (axial diffusion), and more ...
The extended period of cortical myelination in humans may allow greater opportunities for disruption in myelination, resulting in the onset of demyelinating disease. [10] Furthermore, humans have significantly greater prefrontal white matter volume than other primate species, which implies greater myelin density. [11]
Myelination is only prevalent in a few brain regions at birth and continues into adulthood. The entire process is not complete until about 25–30 years of age. [24] Myelination is an important component of intelligence, and white matter quantity may be positively correlated with IQ test results in children. [24]
SVG illustration of the human heart, created by Wapcaplet in Sodipodi. Slightly modified for correct rendering by Yaddah (no changes to content). Cropped version withour white space available at File:Diagram of the human heart (cropped).svg Uploaded on 24 Dec 2003. Diagram of the human heart: Source: Own work: Author: Wapcaplet, Yaddah: Other ...