NEUROGLIA
The neuroglia is a group of a large population of cells of the nervous tissue, called the neuroglial cells or simply glial cells.
These cells do not have the properties of neurons: they are not stimulated and do not react to electrical or chemical stimuli and do not transmit nerve impulses along their extensions. They are also supporting cells of the nervous tissue.
Glial cells perform important functions in the nutrition and trophism of neurons, support of the nervous tissue, and a special population of glial cells acts as macrophages within nervous tissue.
The neuroglial cells are present in the central nervous system. In the peripheral nervous system there are equivalent cells, which some authors include in the classification of neuroglial cells and others consider a separate category.
There are several types of neuroglial cells in the central nervous system:
Astrocytes – their main functions is the support and nourisment of the neurons. There are two main types of astrocytes, called protoplasmic astrocytes and fibrous astrocytes. Protoplasmic astrocytes reside mainly in the gray matter of the central nervous system, while fibrous astrocytes are present mainly in the white matter.
Oligodendrocytes – are present both in the gray matter of the central nervous system and in much greater amount in the white matter of the central nervous system. They surround the axons of neurons and produce myelin.
Microglia – these cells have the capacity to phagocyte and act as macrophages, therefore participating in the defense of nervous tissue.
The diverse astroglial cells are difficult to distinguish and differentiate one from the other in sections submitted to routine staining techniques. For this reason, several techniques have been developed in the past to demonstrate these cells by metallic impregnation, based on the precipitation of metals on them. Nowadays, immunocytochemical methods have been intensively used to recognize and differentiate them.