Glial cells are much more numerous
than neurons. They perform multiple functions. First they keep constant the
ionic environment of the neurons. They also modulate the transmission speed of
the electrical signals. Another function is to modulate synaptic activity
through the control of metabolism of neurotransmitters. Glial cells also have a
scaffolding function in certain stages of development of the nervous system.
Finally, these cells help the recovery of neuronal damage (Parves, Augustine,
Fitzpatrick Hall, LaMantia, White, Neuroscience, Sinauer Associates Inc).
We can divide glial cells into three
types. There are indeed astrocytes, oligodendrocytes and microglia.
Astrocytes have the function of
maintaining an appropriate chemical environment to the transmission of
electrical signals.
Oligodendrocytes, however, create a
lipid coating, called myelin, around some axons. The myelin has the function of
increasing the speed of propagation of nerve signals.
The microglial cells are scavenger
cells that remove cells originating from brain damage or cell replacement. The
microciglia also release signaling molecules that modulate inflammation, cell
death or survival.
Glial cells can also be a stem cell type. They are the astrocytes and the precursors of oligodendrocytes. Astrocytes may produce other stem cells or even neurons, astrocytes or oligodendrocytes. The precursors of oligodendrocytes, however, may produce generally only astrocytes or oligodendrocytes (Parves, Augustine, Fitzpatrick, Hall, LaMantia, White, Neuroscience, Sinauer Associates Inc).
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