In an otherwise healthy individual, what triggers the stimulation of breathing?

The stimulation of breathing in a healthy individual is primarily triggered by an increase in arterial carbon dioxide levels. When carbon dioxide is produced during cellular metabolism, it diffuses from the cells into the bloodstream. As carbon dioxide levels rise, it leads to an increase in hydrogen ion concentration, which in turn lowers blood pH. This change in pH is detected by chemoreceptors, particularly those in the brainstem and carotid bodies.

These chemoreceptors play a crucial role in regulating the respiratory rate and depth. When they sense elevated carbon dioxide levels—often signifying that the body is producing more CO2 than is being expelled through respiration—they stimulate the respiratory centers in the brain. This response enhances the rate and depth of breathing to facilitate the expulsion of carbon dioxide and maintain homeostasis.

In the context of the other choices, while decreased arterial oxygen levels can also influence breathing patterns, it is typically the increase in carbon dioxide that provides a more immediate and direct stimulus for increasing respiration rate. Changes in blood pH that may occur due to other causes (such as metabolic processes) can also influence breathing but are secondary to the effects of carbon dioxide. An increase in tidal volume refers to the amount of air inhaled or exhaled in a