Glial cells are an integral part of the human nervous system. The functions of glial cells include helping to support and nourish nerve cells, or neurons. Several types of glial cells exist.

Glial cells are the “glue” of the nervous system, engaging in many activities to support typical brain function. They do this by facilitating communication between neurons, regulating inflammation and forming the blood-brain barrier.

Each glial cell type has a specific role in supporting the central and peripheral nervous systems. Therefore, dysfunction in glial cells can play a role in developing certain neurological conditions.

This article will provide a comprehensive overview of these cells and their functions.

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Design by MNT; Photography by JAMIE GRILL ATLAS/Stocksy & Science History Images/Alamy Stock Photo

The central nervous system (CNS) consists of the brain and spinal cord, the body’s main control center.

Glial cells are of utmost importance in this region, as they regulate vital functions, such as metabolism, ion balance — or pH balance — and neurotransmission. Neurotransmission refers to how neurons communicate either between themselves or with muscle fibers.

The four primary glial cells of the CNS are below.


The astrocyte is the most abundant type of glial cell in the CNS. They have numerous projections that form a star shape, hence their name.

Although astrocytes exist in different places, they perform similar roles, including:

  • regulating neurotransmitters, which are chemical messengers responsible for cell-to-cell communication
  • forming the blood-brain barrier, a crucial layer of protection for the brain
  • cleaning up the remains of dead neurons and excess potassium ions
  • controlling blood flow to the brain and ensuring that active regions get enough blood
  • synchronizing axon activity so that nerves can communicate properly
  • regulating brain metabolism by storing blood sugar, or glucose, to fuel neurons

Dysfunction of astrocytes has links to some neurological conditions, such as Alzheimer’s disease.


These cells create myelin, a fatty material that wraps around a portion of the nerve cell — called the axon — to insulate them and enable faster electrical conduction.

Faster electrical conduction means impulses, or messages, can travel more efficiently along the neurons.

Oligodendrocytes are essential for proper nerve conduction. They play an important role in certain neurological diseases, such as multiple sclerosis.


Microglia are small, star-shaped cells that help protect the CNS. They are the brain’s resident immune cells and serve as the first line of defense against invading pathogens or disease-causing agents.

Constantly patrolling, these immune cells search for atypical or damaged cells. When the microglia encounter something atypical, they engulf and destroy it with toxic chemicals.

Additionally, microglia help clear out dead cells and debris from the CNS. This process is known as phagocytosis.

Ependymal cells

Ependymal cells develop in the ventricles and fluid-filled compartments of the CNS. They provide the lining for these fluid-filled spaces and help form and transport cerebrospinal fluid (CSF).

The CSF carries chemical messengers, hormones, nutrients, and waste from the brain to the spinal cord and vice versa.

The peripheral nervous system (PNS) consists of the nerves outside the brain and spinal cord. It is responsible for carrying signals to and from the CNS.

Glial cells play an important role in maintaining the health of peripheral nerves and ensuring proper communication between them and the CNS.

Two main types of glial cells develop in this region: Schwann cells and satellite cells.

Schwann cells

Schwann cells are a type of satellite cell that function similarly to oligodendrocytes in the CNS. They create a myelin sheath around nerves, which helps insulate them for faster conduction.

Additionally, these cells help repair damaged axons and can even regenerate them. Stimulating the regeneration of new axons may require the release of growth factors.

Satellite cells

Satellite cells help maintain the health and activity of neurons in the PNS. They provide support and nutrition to peripheral nerves and regulate their calcium levels. These factors are important for proper nerve conduction.

In addition, satellite cells release neurotrophic factors that help protect neurons from degeneration or death. They are essential for developing, maintaining, and repairing peripheral nerves.

Glial cells help support, connect, and protect the neurons of the central and peripheral nervous systems. They come in many shapes, sizes, and types, each performing specialized functions.

In the CNS, glial cells regulate neurotransmission and help form the blood-brain barrier. They also clean up dead neurons, synchronize nerve impulses, and regulate brain metabolism.

In the PNS, Schwann cells create a myelin sheath for faster conduction. Additionally, satellite cells provide nutritional support for neurons.