Breathing Coordination (original) (raw)

Respiration is an important dynamic system which responds to the body's changes in oxygen requirement. The regulation of breathing is controlled by the neurons in the medulla. Under most conditions, breathing rate is maintained involuntarily by the medulla. This system is very flexible and it is possible for breathing rate to be controlled voluntarily. Breathing is accomplished by the medulla firing action potentials at a rhythmical rate. These action potentials cause the muscles in the diaphragm and the intercostal muscles to contract. The rate and depth of breathing is dependent upon the medulla's ability to detect pH levels in the blood. By detecting changes in pH, the medulla is indirectly determining the amount of carbon dioxide in the blood. The following reaction demonstrates the relationship between carbon dioxide levels and pH.

At low pH levels (high [H+]), the respiratory center in the medulla becomes stimulated and results in an increase in the rate and depth of breathing. However when pH is high, breathing becomes slower and shallower due to a decrease in nervous stimulation. For instance in hyperventilation pH levels are so high that there is a temporary cessation of breathing (apnea).

It is possible for a swimmer to remain submerged longer if he/she hyperventilates vigorously before swimming. The purpose of doing this is to remove a maximal amount of carbon dioxide such that the pH level rise dramatically. In response to the high pH levels, the respiratory center stops nervous stimulation of the diaphragm and intercostal muscles to allow the pH to drop to normal levels. By doing this, the individual does not get the urge to surface and breathe. This is a very dangerous practice and can cause drowning.