What does myelin mean?
Myelin is the fatty insulating material that surrounds many nerve fibres, or axons, in the brain, spinal cord, and peripheral nerves. It forms a sheath that limits the leakage of electrical current and supports rapid transmission of nerve impulses. In many axons, the sheath is interrupted at regular intervals, allowing signals to appear to jump from one point to the next, a process called saltatory conduction. This insulation is essential for normal movement, sensation, coordination, and communication within the nervous system. Loss or damage to myelin occurs in conditions such as multiple sclerosis and some forms of peripheral neuropathy. The word is commonly used in medical and biological discussion, especially in expressions such as myelin sheath and myelin damage. It is also a useful term for understanding how nervous-system function depends not only on nerve cells themselves but also on the specialized structures that protect and speed their connections.
nounA fatty insulating substance that forms a sheath around many nerve fibres, helping electrical impulses travel rapidly along the nervous system.
- The fatty material forming an insulating sheath around nerve fibres.
- The myelin sheath itself, especially when discussed in neurology or disease.
"The disease causes the body's immune system to damage the myelin surrounding nerve fibres."
"Myelin damage can interrupt the transmission of signals through the nervous system."
"The microscope revealed a thick layer of myelin surrounding the nerve fibre."
The noun is normally used in the singular or as a mass noun; plural forms such as “myelins” are not standard in general usage.
"The patient has difficulty producing myelin."
Myelin lets nerve impulses leap between gaps in insulation, making the nervous system fast enough to coordinate movement, sensation, and thought.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does myelin come from?
The word comes from Greek myelos, meaning “marrow” or “bone marrow,” through the related scientific combining form myelo-. The term was adopted in the 19th century for the fatty material associated with nerve fibres. Its connection with marrow reflects the historical association of this material with the nervous system and the fatty substance found in marrow, while modern usage specifically identifies it as nerve insulation. The root also appears in related medical and biological words such as myeloid and myeloma.
Related word forms
How myelin is actually used
Usually used as an uncountable mass noun. In medical and biological writing, it commonly occurs with words such as sheath, loss, damage, and disorder. The plural is not normally used.
Easily confused with myelin
Myelin is the insulating material around nerve fibres, whereas myeloma is a cancer of plasma cells in bone marrow.