Glial cells do indeed, as scientists used to think, play the role of glue as they surround neurons and hold them in place Moreover, they supply neurons with fuel – nutrients and oxygen – and act as electricians, building myelin sheaths governing potential transmission along axons. Glial cells have also mastered the profession of janitors by holding back pathogens and eliminating neurons that have ceased all activity. Without these important functions of glial cells, the human brain could not operate as efficiently as it currently does.