The human brain is regarded as the control center for all our activities. The first thought one gets on mentioning brain is the network of nerves and billions of neurons which constitute the nervous system. There are other cells also in the brain called glial cells which are ten to fifty times higher in number as compared to neurons.
These cells are not meant to carry electrical signal or action-potential. But the fact remains that the neurons will be unable to function properly without them. These form the main support system to the entire nervous system. There are different types of these cells and their primary role is to perform a vital role in the nervous system.
One of the most widely known glial cells is called astroglia. These provide supportive structure to the nervous system and also supply nutrients to the neurons. Furthermore, they also perform tasks like janitorial duty, break down dead neural cells and clean up the waste.
Some of the other known glia are astrocyte, microglia, oligodendroglia, satellite cells and Schwann cells.
Astrocytes are star shaped and they give nutritional and physical support to the neurons in the brain. They also perform tasks like cleaning up debris from the brain, transport the nutrients to neurons, assist in holding neurons in their allocated location, digest on parts of neurons that are dead and closely regulate the content in the extra-cellular space.
Microglia is similar to astroglia in digesting parts of neurons which are dead.
Oligodendroglia provides an insulating layer to the neurons called myelin due to transmission over long distances.
Satellite cells are meant to cater for providing physical support to the neurons in the peripheral nervous system. The Schwann cells are earmarked to provide insulation layer called myelin to neurons in the peripheral nervous system.
The oligodendrocytes and the Schwann cells also assist in conducting impulses as the nerves with myelin coating tend to conduct impulses at a faster rate than those without the insulation layer.
Presence of myelin in abundance around neurons in the brain is responsible for the white matter in there. The glial cells get formed from the ectodermal tissue especially the crest and neural tube during the developing stages of the embryo. Microglia is generated by hemopoietic stem cells.
In the central nervous system, glial cells like oligodendrocytes, astrocytes and ependymal cells stem form the ventricular portion of the neural tube, while the glial cells like Satellite and Schwann cells stem from the neural crest.
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