Figure 14-6.

Functions of Astrocytes.

Astrocytes provide structural integrity and regulatory oversight, as depicted in this diagram. They: 1, monitor and regulate fluid and electrolyte balances within neurons and surrounding extracellular space; 2, form the glial limitans at the base of the pia mater; 3, interconnect with other astrocytes to provide a system to monitor and regulate fluid and electrolyte balances throughout the central nervous system (CNS); 4, participate in the formation and functions of the blood-brain barrier; 5, participate in the support of axon tracts of functionally related neurons; 6, monitor for and remove excessive release of neurotransmitters in synapses; 7, protect and insulate nodes of Ranvier; and 8, participate in the cerebrospinal fluid–brain barrier. In addition, astrocytes are a reparative (healing) cell after CNS injury with loss of tissue because nervous tissue, per se, is devoid of fibroblasts. Fibroblasts exist in the meninges and around blood vessels. Everywhere else, healing depends on the astrocyte, which responds by increased length, branching, and complexity of cellular processes (astrogliosis). The astrocyte has many functions in the nervous system; one of them is to act in healing to produce a scar in attempts to isolate cavities and abscesses. Fibroblasts may also contribute to the formation of a scar, if this cell type is present, as it is in the leptomeninges.

(Courtesy Dr. J.F. Zachary, College of Veterinary Medicine, University of Illinois.)