Final answer:
Breathing rates increase with exercise intensity; during moderate and heavy exercise, both the respiratory rate and volume of air per breath increase to meet the body's oxygen demands.
Step-by-step explanation:
Comparing the breathing rates during different levels of activity, such as normal breathing, moderate exercise, and heavy exercise, we observe that breathing rates increase with exercise intensity. Under non-exertion conditions, the average human respiratory rate is 12-15 breaths per minute. During moderate exercise, the respiratory rate and tidal volume (the volume of air per breath) increase to meet the body's higher oxygen demands. With heavy exercise, even higher respiratory rates are observed, alongside increased tidal volumes, to maximize oxygen intake and carbon dioxide expulsion. The respiratory rate is controlled by the respiratory center in the medulla oblongata, which responds to changes in carbon dioxide, oxygen, and blood pH levels.
When ventilation is low, the respiratory rate may increase, while the volume of air per breath may decrease. Conversely, with high ventilation demands, as seen during exercise, the respiratory rate and tidal volume both increase. This adaptation, known as hyperpnea, allows the body to adequately supply oxygen and remove carbon dioxide efficiently during exercise.