Cells {glia}| can provide neuron covering and environment.
covering
Glia cover nerve surfaces, except at synapses and nodes of Ranvier.
structure
Glia provide paths for migrating neurons.
properties
Glia are contractile. Glia can divide. Glia do not conduct. Glia do not interact electrically with neurons. Perhaps, glia are polarizable [Cornell-Bell et al., 1990] [Laming et al., 1998] [Sanderson, 1996].
types
Oligodendrocytes and astrocytes are macroglia. Macrophages are microglia.
chemicals
Glia make myelin, which surrounds axons. Glia make amino acids for neurons. Glia maintain extracellular fluid chemical concentrations. Glia have cholinesterase, whereas neurons have acetylcholinesterase. Glia have much less RNA than neurons.
chemicals: synapses
Glia respond to ATP that leaves synapses by letting calcium in and changing proteins made. Astrocytes make thrombospondin, which builds synapses.
chemicals: regulation
Glia and neuron membranes, receptors, and chemicals interact. Glia regulate extracellular ion, neurotransmitter, and other small-molecule concentrations. Glia can release reactive oxygen molecules, nitric oxide, prostaglandins, excitatory amino acids, IL-1, and nerve growth factor. Excitatory amino acids are N-methyl-D-aspartate and non-NMDA agonists. These can excite pain-responsive spinal cord neurons and increase neurotransmitter release from nerves that relay pain information to spinal cord.
chemicals: factors
Substances released by neurons affect glia [Araque et al., 1999] [DeLeo and Yezierski, 2001] [Raghavendra and DeLeo, 2003] [Watkins et al., 2001].
numbers
Human brains have nine glial cells for every neuron. Glia-to-neuron ratio is as much as 20-to-1 in humans. Glia are half of brain mass. Rats have four or five glial cells for each neuron. The higher human glia-to-neuron ratio reflects need for more chemical and electrical environments and neural connections [Araque et al., 1999] [DeLeo and Yezierski, 2001] [Raghavendra and DeLeo, 2003] [Watkins et al., 2001].
Biological Sciences>Zoology>Organ>Nerve>Glia
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Date Modified: 2022.0224