Final answer:
Breathing rate is chiefly driven by CO2 levels in the blood, monitored by both central and peripheral chemoreceptors that respond to pH and CO2 concentration changes. These chemoreceptors signal the brain to adjust the breathing rate to maintain pH and CO2 homeostasis.
Step-by-step explanation:
The respiratory rate is primarily regulated by the levels of carbon dioxide (CO2) in the blood. This regulation is achieved through chemoreceptors in the central nervous system and in the peripheral vascular system. The central chemoreceptors, located near the respiratory centers in the brain, primarily detect changes in pH caused by alterations in CO2 levels. Peripheral chemoreceptors, found in the carotid arteries and the aortic arch, respond to changes in the concentration of CO2, hydrogen ions (H+), and, to a lesser extent, oxygen (O2).
When CO2 levels rise, it results in an increase of H+ ions, leading to a decrease in blood pH. Chemoreceptors sense this change, stimulating the brain to increase ventilation. This response enhances the removal of CO2 from the bloodstream, which also decreases H+ concentration, thereby raising pH back to normal. Conversely, low CO2 levels result in reduced respiratory rates to balance pH levels.
Through these mechanisms, the respiratory system works continuously to maintain homeostasis in the body, ensuring that the levels of CO2, O2, and pH are kept within optimal ranges.