GLIAL CELLS: what are they, types and functions

When you talk about the brain, you immediately start thinking about neurons and their communication networks. It is true, the brain and the nervous system work because neurons talk to each other, they They touch each other by exchanging information and playing the role of director in the comedy of the lifetime. But what if the glia were missing? In this Psychology-Online article, we will talk precisely about the glial cells, to better understand what they are, the different types and their functions. Let's look at the definition, classification and characteristics of glial cells.

Index

1. What are glial cells
2. Glial cell types
3. Glial cell functions
4. Glial cell structure
5. Differences between neurons and glial cells

The glia, or neuroglia, is the most important cellular component of the nervous system, being 10 to 50 times larger than neurons. The name was introduced in the mid-19th century to indicate the amorphous substance or "nerve cement" that surrounded and supported neurons

By definition, glial cells are a type of cells nervous system that make up, along with neurons, the central and peripheral nervous system. Described for the first time by the German physiologist Rudolf Virchow in 1860, they perform many auxiliary activities to the functioning and survival of neurons, offering them above all a mechanical and nutritional support and exerting a metabolic control of the milieu intercellular.

Just as we can differentiate between several types of neurons, we can also find glial cell types. In the nervous system of vertebrates there are two different types in terms of size and embryonic origin:

Macroglia

The classification of glial cells begins with 3 main types: macroglia and microglia. The macroglia, larger and of neuroectodermal origin, which in the Central Nervous System (SNC) includes astrocytes, oligodendrocytes, and ependymal cells. The latter are the cellular elements that line the cerebral ventricles and the central medullary canal, where they regulate the production, circulation, and resorption of cerebrospinal fluid.

In the peripheral nervous system (SNP), the macroglia is represented by the Schwann cells, equivalent to the central oligodendrocytes and responsible for the formation of the myelin sheaths of the peripheral axons and satellite cells, which outline the outer surface of neurons in ganglia spinal.

Microglia

Microglia, with smaller cells of mesodermic origin, differ from macroglia in size and origin, and represent the population of immunocompetent cells of the central nervous system. The latter have a function similar to that of macrophages and, through the secretion of interleukin, can influence not only the immune response at the level of the nervous system, but also in neuronal activity and reactivity. Microglia represent approximately 10% of the cells of the nervous system and, although present throughout the brain parenchyma, has a variable density from region to region, reaching the highest concentrations in the hippocampus, basal ganglia and the black substance.

The glia cells, in addition to providing support to neurons, control the internal environment of the brain, participate in the formation of specialized structures such as the blood-brain barrier and the sheath myelin, ensure the isolation of nerve cells and their protection against foreign agents or trauma. Other functions performed by glial cells are:

• Collect neurotransmitter molecules extracellular fluid (many glia are equipped with neurotransmitter receptors).
• Compose the blood-brain barrier It actively controls the passage of nutrients and other molecules from the bloodstream to neurons and vice versa.
• During neurobiological development, some specialized glial cells guide the migration of neurons immature to the appropriate places in the brain where they are going to develop, and support the prolongation of the axons towards their target cells.

The fundamental role of the glia in the development and functioning of the nervous system is also reflected in its involvement in many important neuropathologies. The glia are the source of many tumors (called gliomas) of the brain, retina, or spinal cord; in fact, in the brain of the adult animal, they face continuous mitotic divisions, which increases the likelihood of a malignant mutation responsible for proliferation uncontrolled.

After looking at the general functions of glial cells, let's see what each type of glial cell is for:

Satellite cells (SNP)

• They surround the cell bodies in the ganglia.
• They regulate the levels of oxygen and carbon dioxide, nutrients, and neurotransmitters around ganglion neurons.

Shwann cells (SNP)

• Involve axons in the peripheral nervous system
• Responsible for the myelination of peripheral axons
• Participate in damage repair processes

Ependymal cells (CNS)

• They line the encephalic ventricles and the central canal of the spinal cord.
• They contribute to the production, circulation and control of cerebrospinal fluid.

Oligodendrocytes (CNS)

• They myelinate the axons of the central nervous system.
• They provide a structural scaffold.

Astrocytes (CNS)

• They maintain the blood-brain barrier.
• They provide structural support.
• They regulate the concentrations of ions, nutrients and dissolved gases.
• They absorb and recycle neurotransmitters.
• They form scar tissue after injury.

Microglia (CNS)

• Eliminates debris, cell phones, debris and pathogens by phagogitosis.

The most abundant type of glia cells, astrocytes, are made up of numerous excisions that anchor neurons to their blood supply. They are divided into:

• Protoplasmic astrocytes: present in the gray matter and characterized by the presence of short and branched dilations
• Fibrous astrocytes: present in the white matter and characterized by long and subtle cytoplasmic processes.
• Radial astrocytes: elongated and perpendicular to the ventricular axis.

Astrocytes originate in the ectoderm and differentiate by maturing characteristic morphological structures. In general, the shape of the cells is stellate, with a more or less large cell body depending on the type of astrocyte from which numerous filaments are split that allow the cell to have a digitized appearance. These extrudates, of variable size and more or less branched, come into contact with the capillaries brain cells, giving astrocytes the ability to interact with the transport of chemicals to the brain.

The Cellular body and the stellate exsoflesions, called pedicels, can be made up of a variable number of fibrils, called glyofibrils, formed by filaments of small dimensions (approximately 7 nm), the glyo-filaments, which in turn are characterized by small linear subunits.

The glia differ from neurons in several ways:

• Neurons have two types of processes; the glia only has one.
• Neurons can generate action potentialGlial cells do not, but they have a resting potential.
• Neurons have synapse what do they use neurotransmitters; the glia have chemical synapses.
• Neurons do not continue dividing (not the ripe ones, at least); glial cells do.
• Another difference between neurons and glial cells is the amount. There are many more glial cells than neurons (at least 10-50 times more).

This article is merely informative, in Psychology-Online we do not have the power to make a diagnosis or recommend a treatment. We invite you to go to a psychologist to treat your particular case.

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