Which gas concentration primarily influences the control of breathing?

The concentration of carbon dioxide primarily influences the control of breathing because it plays a crucial role in maintaining the body's acid-base balance and is a primary driver of respiration. When carbon dioxide levels increase in the blood, it leads to a decrease in blood pH, creating a more acidic environment. This change is detected by chemoreceptors in the body, particularly in the medulla oblongata and the carotid bodies, which then signal the respiratory centers to increase the rate and depth of breathing in order to expel excess carbon dioxide and restore normal levels.

While oxygen levels are also important for respiration, they are generally monitored in a more secondary role, as the body can tolerate lower levels of oxygen for a short period without significantly influencing the immediate control of breath. Carbon monoxide, although harmful, interferes with oxygen transport and does not directly control the breathing rate. Nitrogen, being an inert gas in respiratory context, does not play a role in stimulating respiration either. Thus, the concentration of carbon dioxide is the key factor that directly regulates the breathing process.