Glial cells, sometimes called neuroglia or simply glia, are non-neuronal cells that maintain homeostasis, form myelin and provide support and protection for neurons in the brain and peripheral nervous system.

 

 

Neuroglia OUN cells

There are four main functions of glial cells

1. Surround the neurons and keep them in place,  2. Supplying nutrients and 3. oxygen to neurons, 4. To isolate one neuron from another, To destroy pathogens and remove dead neurons,


 

 

Types of glial cells

Basically, there are 6 types of glial cells

Macrochic cells, astrocyte, Oligodendroglia, Microglia cells, Schwann Cells, Ependyma Cells, Satellite cells

Glial Cells

 

 

Macroglia

Macrochromic cells include astrocytes, oligodendrocytes, and glioblasts; provide nutrition, physical support, and myelin synthesis. There are two main types of Microglia

 

Astrocytes also are known collectively as astroglia, are characteristic stellate glial cells in the brain and spinal cord. They are the most abundant cells in the human brain.

 

They perform many functions, including biochemical support of endothelial cells that form the blood-brain barrier, provide nutrients to the nervous tissue, maintain the balance of extracellular ions and a role in the repair and scarring of the brain and spinal cord after traumatic injury.

 

 The external chemical environment of neurons by removing excess ions, one of which is potassium and the recycling of neurotransmitters released during synaptic transmission.

 

Current theory suggests that astrocytes may be the dominant “building blocks” of the blood-brain barrier. Astrocytes can regulate vasoconstriction and vasodilation by producing substances such as arachidonic acid whose metabolites are vasoactive.

 

 

Astrocytes signal each other with calcium. Slot connections (also called electrical synapses) between astrocytes allow IP3 relay molecules to propagate from one astrocyte to another. IP3 activates calcium channels on cell organelles, releasing calcium into the cytoplasm.

 

This calcium can stimulate the production of more IP3. The effect of the network is a calcium wave that spreads from the cell.

Extracellular release of ATP and the consequent activation of purinergic receptors on other astrocytes may also mediate in some cases calcium waves.

 

Recently, it has been shown that astrocyte activity is associated with the flow of blood in the brain. Astrocytes can actually communicate with neurons and modify the signals sent and received.

This means that astrocytes are much more involved than previously thought in both information processing and signaling in the synapse.




Oligodendroglia

Their main function Oligodendroglia is to provide support and axonal isolation in the central nervous system of some vertebrates, an equivalent function performed by Schwann cells in the peripheral nervous system. Oligodendrocytes do this by forming a myelin sheath that is 80% lipid and 20% protein.

 

A single oligodendrocyte may extend its processes to 50 axons, wrapping around each axon about 1 μm of myelin sheath; On the other hand, Schwann cells can only wrap around 1 axon. Each oligodendrocyte forms one segment of myelin for several neighboring axons.

 

 

Ependyma Cells

Ependyma is a thin epithelium-like lining of the ventricular system of the brain and the central spinal cord channel and one of the four types of neuroglia in the central nervous system (CNS). It is involved in the production of cerebrospinal fluid (CSF) and is intended as a reservoir for neuroregeneration.

 

 

Satellite cells

Satellite glial cells are glial cells that cover the surface of nerve bodies in sensory, sympathetic and parasympathetic ganglia. Both glial satellite (SGC) and Schwann cells (cells that contain some nerve fibers) come from the nerve’s nerve crest during development.

It was found that SGCs play different roles, including control over the microenvironment of the sympathetic ganglia.