Glial cells

Eva Rudolf-Müller is a freelance writer in the medical team. She studied human medicine and newspaper sciences and has repeatedly worked in both areas - as a doctor in the clinic, as a reviewer, and as a medical journalist for various specialist journals. She is currently working in online journalism, where a wide range of medicine is offered to everyone.

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Glial cells or neuroglia cells make up the cell tissue in the nervous system of the brain. They differ in their structure and function from the other cells in the brain. Glial cells not only form the supporting tissue for the nerve cells, they are also involved in their nutrition and the transmission of information. Read everything you need to know about the various forms of glial cells such as astrocytes and oligodendrocytes, their roles and possible diseases.

What are the glial cells?

The glial cells are the cell tissue that fills the space between the nerve cells of the brain and the blood vessels except for a small gap and that also forms the myelin sheaths around the nerve fibers. The name glia is derived from the Greek word for glue, because the first assumption when researching these cells was that they only had a supporting function for the nerve tissue - that is, the nerve cells would only hold together. It is now known, however, that the glial cells are far more. They demarcate the nerve tissue from the surface of the brain and the blood vessels.

There are several types of glial cells in the nerve tissue of the brain, including:

• Astrocytes or astroglia (star cells with radial projections): belong to the macroglia (large-cell glia) and form most of the glial cells. Mostly found in the gray matter of the brain.
• Oligodendrocytes (small, only slightly branched cells): also belong to the macroglia. Found in the gray and white matter of brain tissue.
• Schwann cells: surround the nerve fibers and form their medullary sheath.
• Microglia cells: have only short processes. Can move in the tissue and absorb foreign bodies and digest them enzymatically (phagocytosis).

What is the function of the glial cells?

The glial cells create the conditions for the nerve cells to be able to work. On the one hand, they fulfill a support function for the nerve tissue of the brain, and on the other hand they are also important for its nutrition.

Another function of the glial cells is phagocytosis - the absorption of particles into the interior of the cell for food intake or for the elimination of foreign bodies.

The transmission of information between the nerve cells is also influenced and controlled by the glial cells. During the embryonic development of the brain, its growth is structured by the glial cells. When the brain is fully grown, these cells ensure that the environment around the nerve cells and nerve fibers (axons) always remains the same. They regulate the pH value, the electrolyte concentration (especially of potassium) and form the myelin sheaths around the axons of the neurons.

Myelin sheaths are like the insulating layer on an electrical cable. They greatly accelerate the transmission of electrical impulses. Oligodendrocytes form the myelin sheaths in the central nervous system (CNS: brain and spinal cord), Schwann cells those in the peripheral nervous system.

Where are the glial cells located?

The glial cells are located throughout the brain and fill the space between the nerve cells and the blood vessels. Their number is far higher than that of the nerve cells in the brain.

What problems can the glial cells cause?

A glioma is the most common malignant brain tumor. It is formed from glial cells in nerve tissue. Depending on the type of glial cells from which the tumor originates, a distinction is made between different forms:

Astrocytoma (especially in the frontal lobe), glioblastoma (most common, in all lobes, subcortical and also in the cerebral cortex), oligodendroglioma (in the hemispheres), oligoastrocytoma and mixed tumors. An optic glioma forms on the optic nerve, a pons glioma on the brain stem. What all tumors have in common is an uncontrolled proliferation of cells.

Ganglion and Schwann cells can be the starting point for a ganglioglioma, a rare, benign brain tumor.

An epileptic seizure is triggered by massive hyperactivity of the nerve cells in the brain. This overactivity significantly increases the potassium concentration in the extracellular space because the glial cells can no longer cope with and absorb the sharp increase.

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