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
Satellite glial cell in nociception. Various neuronal receptors present on SGCs have been named as participants in ATP-evoked pain signals, particularly the homomultimer P2X3 and the heteromultimer P2X2/3 purinoceptors. In general, the P2X family of receptors responds to neuronally released ATP. Each of the P2X subtypes are found in sensory neurons with the exception of the P2X7 receptor, which is selectively expressed by glial cells, including SGCs. The receptor has been implicated in the release of interleukin IL-1β from macrophages or microglia and astrocytes. The receptor likely has a part in the cascade of events that end with inflammation and neuropathic pain. It