Myelin
Myelin serves a very important purpose in the mammalian central nervous system. It is a membrane made from proteins and lipids. In addition to this, myelin is primarily located on axons of neurones (myelin sheath) and in the form of a layer[1].
Myelin prevents the dissipation of the depolarisation wave and current leakage by insulating axon from loss of charged ions (K+), thus allowing an increase of action potential transmission.
Diseases associated with myelin breakdown
And many other demyelinating diseases, where the body's own immune system attacks the myelin forming the myelin sheath and so nerves become un-insulated.