Astrocytes are sub-type of the glial cells in the brain. They are also known as astrocytic glial cells. Star-shaped, their many arms span all around neurons. They are the biggest cells found in brain tissue and outnumber ten_fold the neurons. A fundamental difference with neurons is their ability to duplicate through mitosis.
Functions
A commonly accepted function is to structure physically the brain. A second function is to provides neurons with food such as glucose.
Apparently, they make a second cell network within the brain. Previously in medical science, the neuronal network was considered the only important one, and astrocytes were looked upon as gap fillers. But recently they have been reconsidered. It appears they can actually control communication between neurons by modifying neurotransmitters dispersion. They modify ability for neurotransmitters to go through synapses by isolating the gap or withdrawing from it. This is known as isolation role. Subsequently signal propagation is changed.
Glial cells can communicate independently of the neuronal network. Information moves considerably (100000 times?) slower in the astrocyte network than in the neuronal network, though it could actually complement the fast neuronal information. New exciting perspectives or explanations come with this reconsideration.
Classification
Type I: Those astrocytes are in direct contact with blood capillaries through astrocytique pod. They are actively helping neuronal metabolism and glucose delivery.
Type II: Type II atrocytes surrounds neurones and synaptic gap. This coverage varies from 1 to 100%.
Pictures
A (copyrighted) picture of astrocyte next to a neuron (http://www.denniskunkel.com/PublicHtml/Details_PopUp.asp?File_Name=92751A).
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