The glia cell family is pivotal for neuronal function, and astrocytes are the most numerous glial cells in mammalian brain. By enseathing blood vessels, astrocytes can serve as a conduit for delivery of energetic metabolites to distal neurons during energy consuming processes in addition to buffering excess central nervous system ions and small molecules. In the mature brain, oligodendrocytes increase conduction velocity of larger nerve fibers by enseathing axons between nodes of Ranvier. Microglia, and to a limited extent astrocytes, provide innate immune responses. Arrows represents the flow of nutrients that is taken up by astrocytes from the blood vessels, and transported to surrounding cells.