Astrocytes have a well-developed cytoskeleton that is dominated by intermediate filaments but also includes microtubules and actin filaments, consistent with a role as structural support elements. The proportion of astrocytes in the central nervous system (CNS) increases as the interactions between glial cells and neurons become more sophisticated. Astrocytes have long been regarded as the primary supportive cells of the CNS: they maintain a viable milieu for neurons via their housekeeping functions. However, the data from further studies demonstrated the importance of Glial Fibrillary Acidic Protein in mediating astrocyte-neuron interactions and modulating synaptic activities via astrocytic processes. The pathological events that occur during astrocyte activation and the consequential influences of reactive astrogliosis for the neighboring neural tissue have been under extensive investigation. Astrocytes account for the majority of glial cells in the CNS. Astrocytes, along with microglia, respond to bacterial or viral CNS infections by generating inflammatory responses.