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Grey matter, or brain 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. Grey matter is distinguished from white matter in that it contains numerous cell ...
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.
Myelin. Myelin ( / ˈmaɪ.əlɪn / MY-ə-lin) is a lipid -rich material that surrounds nerve cell axons (the nervous system's electrical wires) to insulate them and increase the rate at which electrical impulses (called action potentials) pass along the axon. [ 1][ 2] The myelinated axon can be likened to an electrical wire (the axon) with ...
Grey matter is composed of cell bodies, dendrites, unmyelinated axons, protoplasmic astrocytes (astrocyte subtype), satellite oligodendrocytes (non-myelinating oligodendrocyte subtype), microglia, and very few myelinated axons. White matter is composed of myelinated axons, fibrous astrocytes, myelinating oligodendrocytes, and microglia.
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.
The cortex is the outermost layer of the brain and consists primarily of gray matter, or neuronal cell bodies. Interior areas of the brain consist of myelinated axons and appear as white matter . Cortical plates
High‑resolution MRI finds the adult human cerebellar cortex has an area of 730 square cm, [12] packed within a volume of dimensions 6 cm × 5 cm × 10 cm. [10] Underneath the gray matter of the cortex lies white matter, made up largely of myelinated nerve fibers running to and from the cortex.
Types. There are four subdivisions of group A nerve fibers: alpha (α) Aα; beta (β) Aβ; , gamma (γ) Aγ, and delta (δ) Aδ. These subdivisions have different amounts of myelination and axon thickness and therefore transmit signals at different speeds. Larger diameter axons and more myelin insulation lead to faster signal propagation.