Neuroglia: Nervous Tissue Glial Cells

Neurons and Glial Cells
Cells of the Brain: neurons are yellow, astrocytes are orange, oligodendrocytes are grey and microglia are white. Credit: JUAN GARTNER/Science Photo Library/Getty Images

What Are Neuroglia?

Neuroglia, also called glial cells, are cells of the nervous system. They compose a voluminous support system that is essential to the proper operation of nervous tissue and the nervous system. Unlike neurons, glial cells do not have axons, dendrites or conduct nerve impulses. Neuroglia are typically smaller than neurons and are about three times more numerous in the nervous system.

Glia perform a plethora of functions in the nervous system. These functions include providing support for the brain, assisting in nervous system repair and maintenance, assisting in the development of the nervous system, insulating neurons, and providing metabolic functions for neurons.

Neuroglia: Nervous Tissue Glial Cells

There are several types of glial cells present in the central nervous system (CNS) and peripheral nervous system of humans. Six main types of neuroglia include:

  • Astrocytes
    Astrocytes are found in the brain and spinal cord. They are star-shaped neuroglia that reside in endothelial cells of the CNS that form the blood-brain barrier. This barrier restricts what substances can enter the brain. Protoplasmic astrocytes are found in the gray matter of the cerebral cortex, while fibrous astrocytes are found in white matter of the brain. Other functions of astrocytes include glycogen storage, nutrient provision, ion concentration regulation, and neuron repair.
  • Satellite Cells
    These glial cells cover and protect neurons of the peripheral nervous system. They provide structure and metabolic support for sensory, sympathetic, and parasympathetic nerves.
  • Oligodendrocytes
    Oligodendrocytes are central nervous system structures that wrap some neuronal axons to form an insulating coat known as the myelin sheath. The myelin sheath, composed of lipids and proteins, functions as an electrical insulator of axons and promotes a more efficient conduction of nerve impulses.
  • Schwann Cells
    Schwann cells are neuroglia that wrap around some neuronal axons to form the myelin sheath in peripheral nervous system structures. Schwann cells help to improve nerve signal conduction, assist in nerve regeneration, and aid in antigen recognition by T cells.

Oligodendrocytes and Schwann cells indirectly assist in the conduction of impulses as myelinated nerves can conduct impulses quicker than unmyelinated ones. Interestingly enough, the white matter in the brain gets its color from the large number of myelinated nerve cells that it contains.

Animal Tissue Types

To learn more about animal tissues, visit:

  • Nervous Tissue  - primary tissue of the central nervous system that is composed of neurons.

Sources:

  • Purves D, Augustine GJ, Fitzpatrick D, et al., editors. Neuroscience. 2nd edition. Sunderland (MA): Sinauer Associates; 2001. Neuroglial Cells. Available from: http://www.ncbi.nlm.nih.gov/books/NBK10869/