In this article, the role of astrocytes in maintaining the neuronal environment in the brain has been explored with reference to health and disease in human beings.
Astrocytes are a type glial cells in the brain and the spinal cord which are star-shaped. They are also known as astrocytic glial cells. They serve many functions, the most important of which are nutrient supply to nervous tissue, biochemical support of endothelial cells which form the blood-brain barrier, maintenance of the balance of the extracellular ions and taking part in the process of repair and regeneration of the central nervous system following various injuries (Magistretti and Ransom, 2008). There re mainly 3 forms of astrocytes. They are fibrous astrocytes, protoplasmic astrocytes and radial astrocytes. Fibrous astrocytes are basically positioned in the white matter. They have few organelles. The cellular processes are 50-60 in number, long and unbranched (Magistretti and Ransom, 2008). When in close proximity, they physically connect the cells to the outerside of the capillary wall. The protoplasmic astrocytes are mainly found in the grey matter of the brain. In contrast to the fibrous cells, they have many organelles and have short, stubby and severely branched cellular processes. These processes are in contact with the blood vessels and also the pial surface. They also surround the neurons. The end-feet of these astrocytes cover the intraparenchymal surface completely and express glucose transporters Glu T type-1 (Magistretti and Ransom, 2008). Thus these cells predominantly function to take-up glucose. Fibrous astrocytes contain more intermediate filaments than protoplasmic astrocytes. The radial glia are mainly found in the vicinity of the ventricles. While some processes abut the piamater, other processes lie deep inside the gray mater. Some examples of radial astrocytes are Bergmann glia cells and Mueller cells of the retina.