Oligodendrocytes are specialized central nervous glia that progress through distinct cellular stages, each with its own specific morphological features, specific proteins, and function. Oligodendrocyte progenitor cells (OPCs) represent the proliferative stem cell population that acts to maintain homeostatic oligodendrocyte numbers and have been shown to respond to neural activity as well as injury and disease. The role that oligodendrocytes play in signal propagation by wrapping axons in a non-conducting sheath represents the most well-known function of myelinating oligodendrocytes.