Human brain the largest cells (by size of cell body) in the nervous system. The adult human brain is estimated to contain 86±8 billion neurons, with a roughly equal number (85±10 billion) of non-neuronal cells. Out of these neurons, 16 billion (19%) are located in the cerebral cortex, and 69 billion (80%) are in the cerebellum. Types of glial cell are astrocytes (including Bergmann glia), oligodendrocytes, ependymal cells (including tanycytes), radial glial cells and microglia. Astrocytes are the largest of the glial cells. They are stellate cells with many processes radiating from their cell bodies. Some of these processes end as perivascular
Glial scar of the injury increase gene expression, thus compounding the response of other astrocytes and contributing to the heterogeneity. Particularly, astrocytes closest to the lesion generally secrete more inhibitory molecules into the extracellular matrix. Microglia are the second most prominent cell type present within the glial scar. They are the nervous system analog of immune system macrophages. Microglia rapidly activate near the injury and secrete several cytokines, bioactive lipids, coagulation factors, reactive oxygen intermediates, and neurotrophic factors. The expression of these molecules depends on the location of the microglial cells relative to the injury, with the cells closest to the injury