Which system is essential for supporting aerobic activity over a long period?

The respiratory system is crucial for supporting aerobic activity over an extended period because it is responsible for the exchange of gases in the body, primarily oxygen and carbon dioxide. During aerobic exercise, the body requires a constant supply of oxygen to generate energy through aerobic metabolism, which takes place in the mitochondria of cells.

As physical activity increases, the demand for oxygen rises, and the respiratory system responds by increasing the rate and depth of breathing. This enhanced ventilation allows more oxygen to enter the lungs and be transported to the bloodstream, where it is delivered to the working muscles. Simultaneously, carbon dioxide, a byproduct of metabolic processes, is expelled more efficiently.

In contrast, while other systems like the nervous, digestive, and endocrine systems play important roles in overall bodily function and during exercise, they do not directly support the specific need for sustained oxygen delivery and carbon dioxide removal during aerobic activities. The nervous system coordinates movement and regulates responses, the digestive system processes nutrients, and the endocrine system releases hormones that can influence energy levels and metabolism, but none of these systems are key to the primary function of sustaining prolonged aerobic activity as is the respiratory system.