Astrocytes are a subtype of a group of brain cells known as glia (which means ‘glue’ in Greek). Glial cells are the most abundant cells in the human brain – outnumbering neurons by a factor of ten to one. Until very recently, glial cells have been thought to be the less exciting sisters of neurones, merely providing them with structural and nutritional support.
Astrocytes have been found to have a unique ability to “taste” the composition of arterial blood entering the brain by sensing increases in arterial levels of carbon dioxide. When activated they release a chemical messenger called ATP which stimulates brain respiratory centres to increase our breathing in order for extra carbon dioxide to be removed from the blood and exhaled.