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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 ...
Latin. incisura myelini. MeSH. D011901. TH. H2.00.06.2.03015. Anatomical terms of microanatomy. [edit on Wikidata] In neuroscience and anatomy, nodes of Ranvier (/ ˈrɑːnvieɪ / RAHN-vee-ay), [1][2] also known as myelin-sheath gaps, occur along a myelinated axon where the axolemma is exposed to the extracellular space.
4. Myelin sheath. 5. Neurilemma. Neurilemma (also known as neurolemma, sheath of Schwann, or Schwann's sheath) [1] is the outermost nucleated cytoplasmic layer of Schwann cells (also called neurilemmocytes) that surrounds the axon of the neuron. It forms the outermost layer of the nerve fiber in the peripheral nervous system.
Cross section of an axon: (1) Axon (2) Nucleus (3) Schwann cell (4) Myelin sheath (5) Neurilemma. In the nervous system, axons may be myelinated, or unmyelinated. This is the provision of an insulating layer, called a myelin sheath. The myelin membrane is unique in its relatively high lipid to protein ratio. [16]
Anatomical terms of microanatomy. [edit on Wikidata] Brain cells make up the functional tissue of the brain. The rest of the brain tissue is the structural stroma that includes connective tissue such as the meninges, blood vessels, and ducts. The two main types of cells in the brain are neurons, also known as nerve cells, and glial cells, also ...
The vertebrate nervous system relies on the myelin sheath for insulation and as a method of decreasing membrane capacitance in the axon. The action potential jumps from node to node, in a process called saltatory conduction , which can increase conduction velocity up to 10 times, without an increase in axonal diameter.
Oligodendrocytes accomplish this by forming the myelin sheath around axons. [1] Unlike Schwann cells, a single oligodendrocyte can extend its processes to cover around 50 axons, [2] with each axon being wrapped in approximately 1 μm of myelin sheath. Furthermore, an oligodendrocyte can provide myelin segments for multiple adjacent axons. [1]
Some clusters of activated microglia, axonal transection and myelin degeneration are present. [7] [8] [9] Leaks in the blood–brain barrier appear and immune cells infiltrate, causing demyelination. [10] and axon destruction. [11] Multiple sclerosis differs from other idiopathic inflammatory demyelinating diseases in its confluent subpial ...