Myelin

In order to understand Multiple Sclerosis and the role Myelin has to play in this disease , some basic facts about the nervous system in the body need to be addressed.

The body's nervous system is made up of two main components: the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). Together, these two systems interact to carry and receive signals that are responsible for nearly every function within the body, including involuntary functions, those a person does not have to consciously think about, such as the beating of the heart or breathing, and voluntary functions such as walking or using your fingers on a computer keyboard to read and scroll up and down this page, which to some extent are consciously thought about .

The Central Nevous System (CNS) is made up of the brain and the spinal cord, and contains billions of specialised cells known as Neurons. Neurons have specific projections called Dendrites and Axons that contribute to their unique function of transmitting signals throughout the body. Dendrites carry electrical signals to the Neuron, while Axons carry them away from the Neuron.

The Peripheral Nervous System (PNS) consists of the rest of the Neurons in the body outside of the Central Nevous System (CNS) . These include the Sensory Neurons, which detect any sensory stimuli and alert the CNS of their presence, and Motor Neurons, which connect the CNS to the muscles and carry out instructions from the CNS for movement.

Picture © John W.Rose, M.D., Maria Houtchens, MSIII, Sharon G. Lynch,M.D.

Myelin
Myelin, is sometimes referred to as "white matter" because of its white, fatty appearance, it protects and insulates the Axons. Myelin consists of a protective sheath of many different molecules that include both lipids (fatty molecules) and proteins. The protective sheath acts in a very similar way to that of the protective insulation that surrounds an electric wire; that is, it is necessary for the rapid transmission of electrical signals between Neurons. It does this by containing the electrical molecules within the Axon so that they are all properly transmitted to the next Neuron.

With the protective Myelin coat, Neurons can transmit signals at speeds up to 60 meters per second.

Picture Copyright © 1997-2005 Mount Sinai Hospital

When the coat is damaged, as with Multiple Sclerosis, the maximum speed can decrease by ten-fold or more, since some of the signal is lost during transmission. This decrease in speed of signal transmission leads to significant disruption in the proper functioning of the nervous system.