Which factor provides the primary stimulus to breathe deeper and faster?
The correct answer and explanation is:
The primary factor that stimulates breathing deeper and faster is the level of carbon dioxide (CO2) in the blood. When CO2 levels increase, it lowers the pH of the blood, making it more acidic. This change is detected by chemoreceptors in the brainstem (specifically the medulla oblongata) and in the carotid and aortic bodies. These receptors are sensitive to the changes in the concentration of CO2 and hydrogen ions in the blood.
When CO2 builds up, the body needs to remove it quickly, so it signals the respiratory centers to increase the rate and depth of breathing. This is a protective mechanism that ensures the body can expel excess CO2 and maintain a normal pH balance. Inhaling deeply and rapidly helps to expel CO2 more effectively, thus returning the blood’s pH to a normal level.
While oxygen levels in the blood can also influence breathing, the body responds more strongly to changes in CO2 than to changes in oxygen. In fact, the body can tolerate low levels of oxygen for a period, but even small increases in CO2 can trigger a strong urge to breathe.
In certain conditions, such as during exercise or when a person holds their breath, CO2 production increases, prompting faster and deeper breathing. Similarly, respiratory diseases like COPD (chronic obstructive pulmonary disease) or emphysema, which impair the ability to expel CO2, can also lead to chronic changes in breathing patterns.
In summary, while multiple factors contribute to regulating the breathing rate, the primary stimulus for breathing faster and deeper is the accumulation of CO2 in the bloodstream.