Astrocytes are generally divided into three subtypes, classified by morphology and anatomic location in the brain: radial, fibrous, and protoplasmic. All astrocytes express varying levels of GFAP, an intermediate filament that bundles together to form gliofilaments. The gliofilaments, 8-12 nm in diameter, are found mainly in the processes and less in the perinuclear region. Astrocytes can be visualized by Golgi impregnation; intracellular dye injection, which allows viewing of the entire cell body and processes; or immunocytochemical staining. Astrocytes are interconnected by gap junctions, which allow intercellular passage of ions and small molecules. The resulting cytoplasmic continuity suggests that astrocytes form a functional syncytium. Gap junctions are also observed between astrocytes and oligodendrocytes but not between astrocytes and neurons. Other characteristic features include the dense granules of glycogen in the cytoplasm and intramembrane "assemblies," observed by freeze fracture electron microscopy. These assemblies consist of 7-nm subunits bundled to form an array in the cell membrane, the function of which is not known. The endfeet of astrocyte processes terminate on the subpial glial limitans, blood vessels, nodes of Ranvier, and axons. Astrocytes are the most abundant cell type in the brain, comprising approximately 55% of the total population, and function in the maintenance of interstitial homeostasis and modulation of synaptic function. Astrocytes respond to almost any central nervous system (CNS) insult by activation and gliosis, which can limit edema, isolate damaged areas, and initiate an immune response.

Breaking Bulimia

Breaking Bulimia

We have all been there: turning to the refrigerator if feeling lonely or bored or indulging in seconds or thirds if strained. But if you suffer from bulimia, the from time to time urge to overeat is more like an obsession.

Get My Free Ebook

Post a comment