Glial cells: The other cells of the nervous system

Carl Ludwig Schleich (1859–1922) was an anaesthetist and a surgeon who for the first time emphasized the role of neuroglia in brain function. In an era that was dominated by the idea that neurons alone were functional units of the nervous system and that glial cells were a mere glue holding neurons in place, Schleich insisted that glia had a prominent functional role to play. He suggested that interactions between neurons and glia were so strong that it is necessary to consider brain as a neuron-glia system whose performance is dependent on both the cell types. Today Carl Ludwig Schleich is considered the forgotten ancestor to a new breed of neurobiologists, the gliologists, who specialize in working on these neglected cells of the nervous system. Though outnumbering the neurons and occupying almost half the volume of the brain, glial cells have been given little importance in textbooks of neurobiology and are very often cursorily mentioned in discussions related to brain function. Glial cells deserve a better deal, for over the years a lot of evidence has accumulated to prove that they perform a wide spectrum of functions. This is the first of a series of articles that aims to update students on what is known about glia today. It provides an overview of the various types of glia and their origins. The following articles will deal with each of the glial sub-types and their functions.