Glial cells are maintenance and support
cells in the central nervous system
(CNS). They are 10 times as numerous as the nerve
cells (neurons) which they look after and make up about half the wieght
of the brain. There are a number of different types of glial cell in
the CNS including: oligodendrocytes,
astrocytes
and microglia. Analogous cells in the Peripheral
Nervous System (PNS) are Schwann and
Satellite cells.
Not all the functions of glial cells are understood but
some of their functions are:
-
Repair and maintenance. Glial cells attempt to keep neurons
heathly. They produce new myelin when it become
damaged (oligodendroctyes) and lay down scar tissue (astroctyes).
-
Physical support. Glial cells have hairlike filaments which
hold the neurons in place and allow the central nervous system to retain
its structural integrity (astrocytes).
-
Central Nervous Sytem development. Glial cells provide an
important function in the early and continuing development of the brain.
-
Chemical regulation. Glial cells supply chemicals such as
potassium
and calcium and regulate neurotransmitter
levels (astrocytes).
-
Cleaning. Glial cells remove dead cells and other debris
from the CNS (astrocytes and microglia).
-
Isolation of the CNS. It used to be thought that glial cells
were important to the Blood Brain Barrier
(BBB) which shields the brain from invasion by pathogens
and other unwanted cells. This function is now disputed and many neurologists
now believe it is performed by the endothelial
cells.
Glial cells, especially oligodendrocytes are often destroyed
at the site of multiple sclerosis lesions. This
postpones or even prevents the repair of the damaged myelin. Working out
how to transport new oligodendrocytes to the site of lesions or growing
new ones from stem cells is the focus of some
of the reseach into new treatments for MS.
Glial cell links:
Neuroscience
for Kids - Glia
Glial
Cells
Glial
cells and growth factors
Glial
Cells and Multiple Sclerosis
Glial
Cells
Protection
of neurons by Glial Cells
Glial
Cells
In
vitro differentiation of embryonic stem cells into glial cells and functional
neurons
MS Glossary
All About Multiple Sclerosis