MS is a disease of the nerves in the central nervous system or CNS. The CNS which consists of the brain and spinal cord, is needed for the input and coordinated from and to all other areas of the body. When the CNS is not functioning properly many systems in the body are affected.
MS is thought to be the result of an autoimmune trigger that causes the body to activate the immune system. Once this trigger occurs inflammatory components of the immune system such as cytokines are able to enter the CNS, which is usually blocked by the blood brain barrier. The blood brain barrier is the body’s way of protecting the CNS against molecules that are not supposed to enter. This leads to inflammation, demyelination, and axonal destruction in the CNS.
Demyelination is the breakdown of the myelin sheath surrounding the nerve fibers that is used to protect the nerves and allows nerve impulses to move faster. Myelin is basically the same thing as insulation that coats electrical wires. When it becomes damaged, the nerve fibers become exposed and the electrical messages traveling down or up the nerve fibers can become diminished. It is important for nerve impulses to move quickly in order to carry messages to and from the CNS and body.
The nerve itself may become injured, furthering the symptoms. Axonal destruction refers to breakdown of the axon, which is the portion of the nerve that carries the message. This results in a reduced the ability of the nerves communicate to each other.
Remission periods are due to the CNS being able to repair the damage from the autoimmune inflammation, reorganize signals, and remyelinate the nerves. Unfortunately the body is not able to compensate for these damages over time and the disease will progress.