What detremental effects does carbon dioxide have on cell membranes and the human brain?
Carbon dioxide reacts in the blood to form carbonic acid and bicarbonate and, if it were allowed to accumulate, would cause acidosis. This condition is particularly harmful to the cells of the brain. Carbon dioxide diffuses into the liquid in the brain, the cerebrospinal fluid (CSF) ; any excess makes it more acid, and this in turn stimulates neural receptors in the brain stem that increase breathing. The result is that the carbon dioxide is blown off in the lungs and the acidity of the blood and brain are kept close to normal levels. Carbon dioxide is the main chemical stimulus to breathing, which is regulated primarily to keep blood and brain acidity at healthy values. If the carbon dioxide in the lungs increases by only 0.2%, from a normal level of about 5%, then breathing is doubled. Breathholding accumulates carbon dioxide in the body, which leads to an irrepressible desire to breathe (lack of oxygen is also a stimulus, but far weaker than carbon dioxide). Conversely, if we volunt
