The Importance Of Glial Cells For The Basic Functions Of The Brain

Before we take a closer look at the importance of glial cells, we can state that the brain is one of the body’s most important organs. It allows us to speak, move, feel and think. Because the brain plays such a central role, much of recent research has focused on understanding which parts it is made up of and how these work.

At first it was thought that our nerve cells (neurons) were the only cells responsible for the activities of the brain. However, recent research has highlighted the importance of glial cells for brain function. As new studies show, glial cells are essential actors in the process that provides for the transfer of information. The studies reveal that some serious brain diseases are not only linked to damage to the nerve cells, but also the glial cells are affected by brain diseases.

The discovery of the importance of glial cells

We can get an idea of ​​how important these small cells are with the help of an example. In several different experiments, attempts were made to isolate nerve cells in culture plates, but the cells always died after a few days. Later, the researchers found that they could make the nerve cells survive by adding an extract of glial cells to the culture medium. In doing so, they illustrated the importance of glial cells for the survival of nerve cells.

In the studies, it was discovered that we have a large number of glial cells or  neuroglia. The name comes from the Greek word “glia”, which means “glue”, plus “neuro”, a term that refers to the brain. In other words, glial cells act as glue in our brains.

Traditionally, glial cells were thought to play a very minor role in the brain. It was assumed that they only acted as a metabolic, structural and trophic (nutritional) support for the nerve cells. However, new research has shown that they fulfill many more functions in various processes that take place in the brain. They often allow other types of nerve cells to perform their tasks.

Functions of glial cells

Glial cells have several functions. Some of these are as follows:

• Insulation. The glial cells produce a substance called myelin, which is needed to isolate nerve cells. Myelin is a dense substance that surrounds the nerve fibers and has the task of protecting the cells and making the transmission of information faster and more efficient. Furthermore, it helps to prevent confusion in the nerve signals. In addition, it plays a crucial role in learning. As shown by various studies, the amount of myelin in the brain increases during the learning process.
• Nutrition source. As we know, the nerve cells in the brain consume a lot of energy. Even if they have a certain nutrient supply, this is not enough to maintain brain activity for more than a few minutes. In this respect , the glial cells help to provide the nerve cells with the nutrition and energy they need. They do this by incorporating energy molecules such as glucose, which they extract from the blood.

• Cleaning. The glial cells remove the waste products associated with nerve cell function. They do this in two ways. On the one hand, it removes the neurotransmitters that remain in the synaptic gap. They convert them and return them to the original nerve cells so that they can once again become raw material for new neurotransmitters. On the one hand, they are responsible for removing the remains of dead nerve cells. This is especially important when the nervous system has been damaged. The cleansing action also helps to alleviate the chemical and physical effects that these residues can cause.
• Synaptic potentiation. The presence of these cells helps to release thrombospondins, which strengthens the synapses, which in turn stimulates synaptic activity.

The significance of glial cells: the different types

There are different types of glial cells and they fulfill a number of different functions. All play important roles in the way brain cells and the brain function.

The glial cells can be classified in different ways. An example is to start from their location in the nervous system. It is this method that we are going to use to describe each of these types.

Central nervous system

First of all, we have astrocytes. These are large, star-shaped glial cells, which is why they have been named macroglia  (large glial cells). These are the most common glial cells in the brain. They surround the synaptic connections in the brain.

One of their main functions is to define cell boundaries and help create a defense barrier for the brain. Furthermore, they control the formation of synapses and their function, neurogenesis and the regulation of muscle tone. At the same time, they also help to nourish nerve cells.

Then there are oligodendrocytes. They are macroglia of the central nervous system. They are important for the isolation of cells by supplying the nerve fibers with myelin. These cells have the ability to myelinate more is a nerve fiber and sometimes they can even regenerate damaged nerve fibers.

Finally, one finds the microgia cells, microglia, which participate in the brain’s cleansing processes. They respond when damage occurs to the system by removing cell debris and triggering the brain’s inflammatory response.

Peripheral Nervous System (PNS)

In this part of the nervous system, it is the Schwann cells, which are macroglia, that take over. These glial cells are divided into three subgroups. The first type is the one that forms myelin. As the name suggests, they help to myelinate the nerves, but they can only do so with one nerve at a time. When brain damage occurs, their task is to cleanse the system and promote regeneration.

The second type is Schwann cells that do not form myelin. We do not yet know how these cells communicate with the nerve fibers. However, studies have shown that they are necessary for the function and maintenance of the non-myelinated nerve fibers. These nerve fibers are important in creating pain experiences.

In the third group we find perisynaptic Schwann cells. These cells cover the neuromuscular junctions and release neurotransmitters and peptides. The receptors located in their membranes allow them to send signals relating to these substances. They can also control and strengthen the synapses.

In short, glial cells are a fundamental part of the nervous system. Not only do they support the cells, but they also help in activities related to synapses, cleansing and nutrition. Therefore, they have a major impact on the development of certain diseases, including multiple sclerosis.