Neuroglia (Glial cells)
Glial cells, sometimes called neuroglia or simply glia, are non-neuronal cells that maintain homeostasis, form myelin, and provide support and protection for neurons in the brain and peripheral nervous system.
Figure 1 Neuroglia cells of the CNS
There are four main functions of glial cells:
- To surround neurons and hold them in place
- To supply nutrients and oxygen to neurons
- To insulate one neuron from another
- To destroy pathogens and remove dead neurons
The Table below lists those natural substances that enhance the glial cells:
Types of Glia
There are generally 6 types of glial cells:
- Macroglial Cells
- Microglia Cells
- Schwann Cells
- Ependyma Cells
- Satellite Cells
Figure 2 Types of Neuroglia
Macroglia cells include astrocytes, oligodendrogliocytes and glioblasts; they provide nutrition, physical support and synthesise myelin.
There are two main types of Macroglia:
Astrocytes (Astro from Greek astron = star and cyte from Greek “kyttaron” = cell), also known collectively as astroglia, are characteristic star-shaped glial cells in the brain and spinal cord. They are the most abundant cells of the human brain. 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.
Figure 3 Astrocyte
They regulate the external chemical environment of neurons by removing excess ions, the notable one being potassium, and recycling neurotransmitters released during synaptic transmission. The current theory suggests that astrocytes may be the predominant “building-blocks” of the blood–brain barrier. Astrocytes may regulate vasoconstriction and vasodilation by producing substances such as arachidonic acid, whose metabolites are vasoactive.
Astrocytes signal each other using calcium. The gap junctions (also known as electrical synapses) between astrocytes allow the messenger molecule IP3 to diffuse from one astrocyte to another. IP3 activates calcium channels on cellular organelles, releasing calcium into the cytoplasm. This calcium may stimulate the production of more IP3. The net effect is a calcium wave that propagates from cell to cell. Extracellular release of ATP, and consequent activation of purinergic receptors on other astrocytes, may also mediate calcium waves in some cases.
It has recently been shown that astrocyte activity is linked to blood flow in the brain.
Astrocytes can actually communicate with neurons and modify the signals they send and receive. That means astrocytes are much more involved than once thought in both the processing of information, and the signaling at the synapse.
Figure 4 Astrocytes communicate with neurons
The Table below lists those natural substances that enhance astrocytes:
Substances that Enhance the Astrocytes
Category Substance Reference
Herbs Korean Ginseng 1
Hormones Melatonin 2
Nootropics Idebenone 3
Organic Acids Rosmarinic Acid 6
Peptides Carnosine 7
Vitamins Vitamin D 8
Oligodendrocytes are cells that coat axons in the central nervous system (CNS) with their cell membrane, forming a specialized membrane differentiation called myelin, producing the so-called myelin sheath. The myelin sheath provides insulation to the axon that allows electrical signals to propagate more efficiently.
Figure 5 Oligodendrocyte
Their main functions of Oligodendroglia are to provide support and insulation to axons in the central nervous system of some vertebrates, equivalent to the function performed by Schwann cells in the peripheral nervous system. Oligodendrocytes do this by creating the myelin sheath, which is 80% lipid and 20% protein.
A single oligodendrocyte can extend its processes to 50 axons, wrapping approximately 1 μm of myelin sheath around each axon; Schwann cells, on the other hand, can wrap around only 1 axon. Each oligodendrocyte forms one segment of myelin for several adjacent axons.
Figure 6 Oligodendrocyte wrapping mylein sheath around each axon
The Table below lists those natural substances that enhance the Oligodendroglia:
Microglia are specialized macrophages capable of phagocytosis that protect neurons of the central nervous system. Microglia act as the first and main form of active immune defense in the central nervous system (CNS). They are derived from hematopoietic stem cells in mesodermal tissue; they are commonly categorized as such because of their supportive role to neurons.
These cells are found in all regions of the brain and spinal cord. Microglial cells are small relative to macroglial cells, with changing shapes and oblong nuclei. They are mobile within the brain and multiply when the brain is damaged. In the healthy central nervous system, microglia processes constantly sample all aspects of their environment (neurons, macroglia and blood vessels).
Microglia constitute 10-15% of all cells found within the brain.
Figure 7 Microglia
The Table below lists those natural substances that enhance the Microglia:
Schwann cells provide myelination to axons in the peripheral nervous system (PNS). They also have phagocytotic activity and clear cellular debris that allows for regrowth of PNS neurons.
There are two types of Schwann cell, myelinating and nonmyelinating. Myelinating Schwann cells wrap around axons of motor and sensory neurons to form the myelin sheath.
Figure 8 Schwann cells
Schawann cells are involved in many important aspects of peripheral nerve biology—the conduction of nervous impulses along axons, nerve development and regeneration, trophic support for neurons, production of the nerve extracellular matrix, modulation of neuromuscular synaptic activity, and presentation of antigens to T-lymphocytes.
Figure 9 Schwann cell nucleus
The Table below lists those natural substances that enhance Schwann cells:
Substances that Enhance the Schwann Cells
Schwann Cells Category Substance Reference
Alkaloid Berberine 1
Herbs Ginko Biloba 2
Korean Ginseng 3
Lipids Forskolin 4
Minerals Zinc 5
Polyphenols Quercetin 6
Vitamins Vitamin B12 7
Pyrroloquinoline Quinone 8
Ependyma is the thin epithelial-like lining of the ventricular system of the brain and the central canal of the spinal cord. Ependyma is one of the four types of neuroglia in the central nervous system (CNS). It is involved in the production of cerebrospinal fluid (CSF), and is shown to serve as a reservoir for neuroregeneration.
Satellite glial cells are glial cells that cover the surface of nerve cell bodies in sensory, sympathetic and parasympathetic ganglia. Both satellite glial cells (SGCs) and Schwann cells (the cells that ensheath some nerve fibers) are derived from the neural crest of the embryo during development. SGCs have been found to play a variety of roles, including control over the microenvironment of sympathetic ganglia.
The Table below is a summary of the natural substances and the various types of neuroglia:
Summary of Substances that Enhance the Function of the Neuroglia
Category Substance Glial Astrocytes Oligodendroglia Microglia Schwann Cells #
Alkaloid Berberine X 1
Amino Acids N-Acetyl-Cysteine (NAC) X 1
Herbs Korean Ginseng X X 2
Ginko Biloba X 1
Hormones Melatonin X 1
DHEA X 1
Lipids GLA X 1
Forskolin X 1
Minerals Zinc X 1
Nootropics Nicergoline X 1
Vinpocetine X 1
Deprenyl X 1
Piracetam X 1
Idebenone X 1
Peptides Carnosine X 1
Polyphenols Curcumin X 1
Quercetin X 1
Organic Acids Rosmarinic Acid X Quinones Coenzyme Q10 X 1
Vitamins Vitamin C X 1
Vitamin D X X 2
Vitamin K X 1
Vitamin B12 X 1
Pyrroloquinoline Quinone X 1
BioFoundations – Natural Substances that Enhance the Integrity and Function of the Neuroglia (Glial cells) (PDF)
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Video: Types of Neuroglia (Glial Cells) by AKLectures
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