Glial Cells
Overview
Glial cells, also known as neuroglia or simply glia, are non-neuronal cells in the central nervous system (CNS) and the peripheral nervous system (PNS). They provide support and protection for neurons, the other main type of cells in the nervous system. Unlike neurons, glial cells do not conduct electrical impulses. Instead, they maintain homeostasis, form myelin, and provide support and protection for neurons.
Types of Glial Cells
There are several types of glial cells, each with a unique function and location within the nervous system. These include astrocytes, oligodendrocytes, microglia, ependymal cells, Schwann cells, and satellite cells.
Astrocytes
Astrocytes are star-shaped glial cells in the brain and spinal cord. They perform many functions, including biochemical support of endothelial cells that form the blood-brain barrier, provision of nutrients to the nervous tissue, maintenance of extracellular ion balance, and a role in the repair and scarring process of the brain and spinal cord following traumatic injuries.
Oligodendrocytes
Oligodendrocytes are a type of glial cell that reside in the CNS. They are responsible for the formation of myelin, a fatty substance that insulates nerve fibers and allows for efficient transmission of electrical signals along the nerve cells.
Microglia
Microglia are a type of glial cell located throughout the brain and spinal cord. They act as the first and main form of active immune defense in the CNS. Microglia are constantly scavenging the CNS for plaques, damaged neurons, and infectious agents.
Ependymal Cells
Ependymal cells line the cerebrospinal fluid (CSF)-filled ventricles in the brain and the central canal of the spinal cord. They are involved in the production, transport, and removal of CSF.
Schwann Cells
Schwann cells are a variety of glial cell that keep peripheral nerve fibers alive. In the PNS, Schwann cells also have the ability to form myelin.
Satellite Cells
Satellite cells are small glial cells that provide structural support to the neurons in the peripheral nervous system. They also regulate the external chemical environment.
Functions of Glial Cells
Glial cells perform a variety of functions in the nervous system, including:
- Providing support and nutrition
- Insulating neurons
- Destroying pathogens and removing dead neurons
- Modulating neurotransmission
- Forming the blood-brain barrier
Glial Cells and Disease
Abnormalities or changes in glial cells have been linked to a number of neurological disorders, including multiple sclerosis, Alzheimer's disease, Parkinson's disease, and Amyotrophic Lateral Sclerosis (ALS). Research into the role of glial cells in these conditions is ongoing, and it is hoped that a better understanding of these cells may lead to new treatments.