Astrocyte Neurobiology

Astrocytes are special glial cells by a population of about 10 times more than the population of the neuron within the central nervous system (CNS) as they occupy almost the 25% to 50% of the brain volume. They are apparently stellar in shape and have many processes enabling them to produce non synaptic contacts with neural cells. Using perivascular feet they are covering near to 85% of CNS capillaries external surface. Astrocytes are arranged like building blocks all over the CNS and connected to each other by Gap junctions producing an electrical syncytiym. In the previous knowledge of medicine، within the CNS and between the glial cells، microglia were considered as more important player than the Astrocytes، as Astrocytes were seen merely as guard cells and filler of empty spaces in the CNS. However studies at the last 20 years were clarified that the Astrocytes are important not only for physical support and neural nourishment but also for neural system development and synapse formation، neural tissues blood current and energy regulation، neurotransmitter adjustment and even immunological responses within the CNS. The present article is to review and point on the different roles of Astrocytes within the CNS.