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 the same sheath (reflexive gap junctions). These gap junctions have been identified through the use of electron microscopy and weight tracer markers, such as Lucifer yellow or neurobiotin. The degree to which SGCs are coupled to SGCs of another sheath or to SGCs of the same sheath is dependent on the pH of the cellular environment. From studies on rats and mice, researchers have found that satellite glial cells express many neurotransmitter receptors, such as muscarinic acetylcholine and erythropoietin receptors. In order to differentiate between SGCs and other glial cells researchers have used markers to identify which proteins are