myelin /my·elin/ (mi´ĕ-lin) the lipid-rich substance of the cell membrane of Schwann cells that coils to form the myelin sheath surrounding the axon of myelinated nerve fibers.myelin´ic
Myelin
myelin
myelin [mi´ĕ-lin]
my·e·lin (m   -l n) or my·e·line (-ln, -l n )n. 1. A white fatty material composed chiefly of alternating layers of lipids and lipoproteins that encloses the axons of myelinated nerve fibers. 2. Droplets of lipid formed during autolysis and postmortem decomposition. my e·linic adj. |
Myelin
A whitish fatty substance that acts like an electrical insulator around certain nerves in the peripheral nervous system. It is thought that the loss of the myelin surrounding the vestibular nerves may influence the development of Ménière's disease.
Mentioned in: Adrenoleukodystrophy, Charcot Marie Tooth Disease, Guillain-Barré Syndrome, Ménière's Disease, Multiple Sclerosis, Paralysis, Peripheral Neuropathy, Phenylketonuria
myelin
[mī′əlin]
Etymology: Gk, myelos, marrow
a lipoproteinaceous substance constituting the sheaths of various nerve fibers throughout the body and enveloping the axis of myelinated nerves. It is largely composed of phospholipids and protein, which gives the fibers a white, creamy color. myelinic, adj.
myelin [mi´ĕ-lin]
the lipid substance forming a sheath (the myelin sheath) around the axons of certain nerve fibers; it is an electrical insulator that serves to speed the conduction of nerve impulses in these nerve fibers, which are called myelinated or medullated fibers. adj., adj myelin´ic.
Myelinated nerve fibers occur predominantly in the cranial and spinal nerves and compose the white matter of the brain and spinal cord. Unmyelinated fibers are abundant in the autonomic nervous system. The term gray matter refers to areas in the nervous system in which the nerve fibers are unmyelinated. In unmyelinated nerves impulses are conducted by the propagation of the action potential along the membrane of the axon. In myelinated nerves impulses are transmitted by an entirely different process, called saltatory conduction, in which the impulse jumps from one node of ranvier to the next. Impulses in myelinated nerves are transmitted hundreds of times faster and require much less energy than in unmyelinated nerves.
Myelinated nerve fibers occur predominantly in the cranial and spinal nerves and compose the white matter of the brain and spinal cord. Unmyelinated fibers are abundant in the autonomic nervous system. The term gray matter refers to areas in the nervous system in which the nerve fibers are unmyelinated. In unmyelinated nerves impulses are conducted by the propagation of the action potential along the membrane of the axon. In myelinated nerves impulses are transmitted by an entirely different process, called saltatory conduction, in which the impulse jumps from one node of ranvier to the next. Impulses in myelinated nerves are transmitted hundreds of times faster and require much less energy than in unmyelinated nerves.
Structure of a typical myelin sheath. From Applegate, 2000.
myelin (mī·l
n),n a white fatty material that constitutes the medullary sheath that surrounds some nerve fibers.
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Myelin.
myelin (mī´
lin),n a fatlike substance forming a sheath around certain nerve fibers. It is associated with volitional nervous system fibers and is believed to be related to the capacity of nerve structures for rapid transmission of nerve impulses. Various diseases, such as multiple sclerosis, can destroy these myelin wrappings.
myelin
1. the lipid substance forming a sheath around the axons of certain nerve fibers; these nerve fibers are spoken of as myelinated or medullated fibers.
2. lipoid substance found in various normal and pathological tissues, which differs from fats in being doubly refractive.
Myelinated nerve fibers occur predominantly in the cranial and spinal nerves and compose the white matter of the brain and spinal cord. It is the myelin sheath that gives the whitish color to the areas of white matter. Unmyelinated fibers are abundant in the autonomic nervous system.
Patient discussion about myelin.
Q. What is Myelin?
A. Myelin is a phospholipid layer that surrounds only the axons of many neurons. The main role of a myelin layer (or sheath) is an increase in the speed at which impulses pass along the myelinated fiber. Demyelination is the act of demyelinating, or the loss of the myelin sheath insulating the nerves, and is the cause of some neurodegenerative autoimmune diseases, including multiple sclerosis, acute disseminated encephalomyelitis, transverse myelitis, Alexander's disease, chronic inflammatory demyelinating polyneuropathy, Guillain-Barré Syndrome and central pontine myelinosis. Here is a link to a website that tells more about it:
http://www.myelin.org/
Read more or ask a question about myelinhttp://www.myelin.org/
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