What action occurs in the body during hyperventilation?

During hyperventilation, the primary action that occurs is an increased expulsion of carbon dioxide (CO2) from the body. Hyperventilation is characterized by rapid and deep breathing, which leads to a greater amount of CO2 being exhaled. As a result of this excessive loss of CO2, the concentration of CO2 in the blood decreases, which can lead to respiratory alkalosis—a condition where the pH of arterial blood rises, making it more alkaline.

This process can also affect the levels of oxygen in the blood, but the primary change during hyperventilation is the dramatic decrease in CO2, rather than a rapid decrease in oxygen levels. While it is possible for blood oxygen levels to rise slightly due to increased lung ventilation, this is not the main focus of hyperventilation's physiological effects. The other options, like retention of CO2 and a decrease in blood pH, do not occur in hyperventilation but rather are associated with conditions where breathing is inadequate, such as hypoventilation or respiratory failure.