The differences in the myelination processes of the central nervous system and the peripheral nervous system are the structures that generate the myelin sheaths. The sheaths are formed by oligodendrocytes in the CNS and by Schwann cells in the PNS, according to Jorge A. Pereira in Trends in Neurosciences.
Myelin sheaths protect the nervous tissue cells, which carry the biochemical signals from the sensory organs to the brain as well as protect the cells of the brain. They are formed when oligodendrocytes (in the CNS) and Schwann cells (in the PNS) envelope the axons of nerve cells and wrap them in myelin fibers. Both types of cells wrap their plasma membranes around the axons and arrange approximately 10 layers of myelin fibers, creating the recognizable layered appearance associated with the cells, according to Trends in Neurosciences.
The functionality of this system is critical to health. Failure of any of the systems associated with the myelination process results in debilitating and potentially fatal disorders, including Tay-Sachs disease and multiple sclerosis. Symptoms of such illnesses are usually progressive, being almost unnoticeable in the formative stages, but they gradually impede the patent's ability to function until death results, as described by the article "Demyelinating Diseases" in the Journal of Clinical Pathology.