Myelin and the Central Nervous System (cont.)
IN THIS ARTICLE
What is myelin?
Myelin is a fatty material that coats, protects, and insulates nerves, enabling them to quickly conduct impulses between the brain and different parts of the body. Myelin also contains proteins that can be targeted by the immune system. Myelin coats the nerves of both the central nervous system and the peripheral nervous system; the destruction of the myelin in the central nervous system is what triggers many of the symptoms of multiple sclerosis (MS).
Nerve cells are coated with sections of myelin, and the tiny spaces between the sections are called nodes. As the brain sends messages through the nerves of the spinal cord, the impulses jump from node to node. Myelin prevents these impulses from escaping from the nerve at the wrong point.
In multiple sclerosis, T cells from the body's own immune system attack and destroy the myelin sheath, leaving the nerve cell fibers unprotected.
How is myelin destroyed?
In multiple sclerosis (MS), the body's immune system T cells attack the myelin sheath that protects the nerve fibers. The T cells either partially or completely strip the myelin off the fibers, leaving the nerves unprotected and uninsulated. The nerves are not as able to pass messages from the brain to the other body parts. The messages the nerves try to send are delayed or distorted and the messages the brain receives may be misinterpreted.
Myelin is lost in multiple areas, leaving scar tissue that due to its hardened characteristics is called sclerosis. These damaged areas where the myelin has been destroyed and further disrupt the ability for the nerves to pass messages are also called plaques. These plaques can be identified by magnetic resonance imaging (MRI), a technique that helps doctors assess and monitor the progression of multiple sclerosis.
What happens when myelin is destroyed?
When myelin is destroyed, the transmission of nerve impulses is impaired. Messages do not get through quickly and clearly from the brain to the correct body part. The more myelin is destroyed, the slower and less efficient the nerve impulses are. Depending on the severity of the immune system attack, the nerve fibers themselves may be damaged or destroyed. (See Multimedia file 1). Damage to nerve fibers may play an important role in determining how severe disability in multiple sclerosis may become.
When the brain nerves do not communicate well with nerves from other areas of the central nervous system (brainstem or spinal cord) or cannot relay information to nerves that exit these structures (peripheral nervous system), the symptoms of multiple sclerosis can occur.
For More Information
Medically reviewed by Jon Glass, MD; American board of Psychiatry and Neurology
Medically Reviewed by a Doctor on 8/1/2014
Fernando Dangond, MD
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Charcot-Marie-Tooth (CMT) disease was first recognized independently in France and Great Britain (Charcot and Marie, 1886; Tooth, 1886).