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The nerve cells, known as neurons, carry impulses throughout the body and the nerve impulses are carried along the axon. These microscopic nerve fibers, where the action potential occurs, are protected by a white, fatty tissue that surrounds and insulates it, known as the myelin sheath.
A demyelinating disease refers to any disease affecting the nervous system where the myelin sheath surrounding neurons is damaged. [1] This damage disrupts the transmission of signals through the affected nerves, resulting in a decrease in their conduction ability.
When an axon is damaged, the distal segment undergoes Wallerian degeneration, losing its myelin sheath. The proximal segment can either die by apoptosis or undergo the chromatolytic reaction, which is an attempt at repair. In the CNS, synaptic stripping occurs as glial foot processes invade the dead synapse. [1]
The myelin sheath that surrounds and protects nerve cells is made by cells called oligodendrocytes. In a person with MS, these cells are lost, so damaged myelin sheaths cannot be repaired.
Myelin (/ ˈ m aɪ. ə l ɪ n / MY-ə-lin) is a lipid-rich material that surrounds nerve cell axons 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 insulating material (myelin) around it. However ...
The T cells recognize myelin as foreign and attack it, explaining why these cells are also called "autoreactive lymphocytes". Demyelination, further inflammation and axonal transection are the result. The attack of myelin starts inflammatory processes, which triggers other immune cells and the release of soluble factors like cytokines and ...
Axonal degeneration is followed by degradation of the myelin sheath and infiltration by macrophages. The macrophages, accompanied by Schwann cells, serve to clear the debris from the degeneration. [5] [6] Schwann cells respond to loss of axons by extrusion of their myelin sheaths, downregulation of myelin genes, dedifferentiation and proliferation.
Myelin sheath of a healthy neuron in the central nervous system. Multiple sclerosis is an inflammatory demyelinating disease of the CNS in which activated immune cells invade the central nervous system and cause inflammation, neurodegeneration, and tissue damage. The underlying cause is currently unknown.