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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.
In the central nervous system (brain, spinal cord and optic nerves), myelination is formed by specialized glial cells called oligodendrocytes, each of which sends out processes (limb-like extensions from the cell body) to myelinate multiple nearby axons; while in the peripheral nervous system, myelin is formed by Schwann cells (neurolemmocytes ...
Myelinated axons (right) conduct impulses faster than unmyelinated axons. The function of nervous tissue is to form the communication network of the nervous system by conducting electric signals across tissue. [13] In the CNS, grey matter, which contains the synapses, is important for information processing.
There are two types of axons in the nervous system: myelinated and unmyelinated axons. [5] Myelin is a layer of a fatty insulating substance, which is formed by two types of glial cells: Schwann cells and oligodendrocytes. In the peripheral nervous system Schwann cells form the myelin sheath of a myelinated axon. Oligodendrocytes form the ...
A single oligodendrocyte can extend its processes to cover up to 40 axons, that can include multiple adjacent axons. [2] The myelin sheath is not continuous but is segmented along the axon's length at gaps known as the nodes of Ranvier. In the peripheral nervous system the myelination of axons is carried out by Schwann cells. [1]
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.
White matter refers to areas of the central nervous system (CNS) that are mainly made up of myelinated axons, also called tracts. [1] Long thought to be passive tissue, white matter affects learning and brain functions, modulating the distribution of action potentials , acting as a relay and coordinating communication between different brain ...
Schwann cells are a variety of glial cells that keep peripheral nerve fibres (both myelinated and unmyelinated) alive. In myelinated axons, Schwann cells form the myelin sheath. The sheath is not continuous. Individual myelinating Schwann cells cover about 1 mm of an axon [3] – equating to about 1000 Schwann cells along a 1-m length of the axon.