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Astrocytes: definition, appearance and general physiology 2

Part 2 of 2
Published on April 28, 2022   30 min

A selection of talks on Cell Biology

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0:03
Now, we are coming to mechanisms of excitability of astrocytes. By definition, astrocytes are electrically non-excitable cells. This means that they cannot produce a regenerative action potential. That, of course, is a function of neurons in the nervous system. However, astrocytes do have their own mechanism of excitability, which is represented by changes in the cytosolic concentration of ions and second messengers. Of course, ion number one which is a reversal second messenger in many different cells, tissues practically all over the universe or the living universe on Earth, this is calcium.
0:49
Let me start with a small historical digression. Calcium had been discovered by Professor Humphry Davy in 1808. That is the reason for the name is because Humphry Davy demonstrated that lime is a combination of metal and oxygen; hence, calcium from the Latin word 'calx' for chalk. The biological importance of
1:14
calcium ions had been found some years later. That was Sydney Ringer, who, in the 1880s, performed several experiments in different tissues and species which demonstrated incredible importance at this time. One of his most amazing experiments was also extremely simple. He took some fish from the fish market in London and put them in normal tap water. Normal tap water was from the Thames and, of course, it had everything and those animals survived without any major problems. But then he transferred some of these fish into distilled water, which doesn't have calcium, and these animals started to die very slowly. In order to rescue them, the only thing that was necessary to do was to add a minor amount of calcium into the distilled water. That was the very first experiment that demonstrated the importance of calcium as an ion of life and death.

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