Myelin Sheath


Also found in: Dictionary, Thesaurus, Medical, Wikipedia.

myelin sheath

[′mī·ə·lən ′shēth]
(neuroscience)
An investing cover of myelin around the axis cylinder of certain nerve fibers.

Myelin Sheath

 

(medullary substance; medullary sheath), the sheath enclosing the medullated nerve fibers. The outside of the myelin sheath is covered with a plasma membrane of the Schwann cell; inside, it borders the surface membrane of the axon—the axolemma.

It is believed that the myelin sheath consists of myelin, which includes biomolecular layers of lipides (a phosphatide-cholesterol complex and other chemical components) and coaxially distributed monomolecular layers of protein. The myelin sheath forms as a result of the envelopment of the nerve-cell process by Schwann cells. In the vicinity of the nodes of Ranvier, the myelin sheath is interrupted; the area between any two nodes is formed by a single Schwann cell. The myelin sheath prevents the scattering of nerve impulses and their transfer to other nerve fibers. Impulses are conducted more rapidly in medullated nerve fibers than in nonmedullated ones.

References in periodicals archive ?
When they took this experiment to a larger scale, in the actual mouse, the researchers found that mice treated with these melanocyte stem cells had myelin sheath structures in the brain as opposed to untreated mice who lacked these structures.
The findings of significantly smaller nerve and axon diameters and a thinner myelin sheath in the control group may point to the fact that both melatonin and dexamethasone had important effects in reducing nerve degeneration.
Almeida et al., "Synaptic vesicle release regulates myelin sheath number of individual oligodendrocytes in vivo," Nature Neuroscience, vol.
Also, the Thickness of the myelin sheaths of control and OGD offspring showed no significant difference (Figs.1-3 and Table I).
In the experimental group, on Day 28 after operation (Figure 2(d)), the shape and diameter of the axons and also the thickness of the myelin sheath were similar to
To analyze the fate of eGFP-[SCs.sup.N] and eGFP-[SCs.sup.I] after the transplantation, triple fluorescence observations after double immunofluorescence staining to NF-200 for axon and P0 for myelin sheath were performed in the cross sections (Figure 2(c)).
Additionally, the myelin sheath is made thinner and in some cases absent (Figures 1(e) and 1(f)).
Key words: Nerve fiber myelin sheath axon cerebellar white matter; D-galactose INTRODUCTION
Within that group, researchers found only 25 patients had received any vaccine in the six weeks before the onset of Guillain-Barre, an acute disease that results in destruction of a nerve's myelin sheath and peripheral nerves.
There are medications that can help reduce the impact of the disease, such as glatiramer, which helps prevent the body's immune system from attacking the myelin sheath around nerve fibers.
9:15 EFFECTS OF LIGHT EXPOSURE AND VITAMIN D ON THE DEVELOPMENT OF MYELIN BASIC PROTEIN IN THE MYELIN SHEATH OF NEURONAL AXONS IN JUVENILE ZEBRAFISH **, Callie Holloway * and Linda G.
In the human body what are protected by the myelin sheath? 6.