Final answer:
During moderate exercise, ventilation increases resulting in a higher rate and depth of breathing to clear the increased carbon dioxide produced by muscles, which is referred to as hyperpnea.
Step-by-step explanation:
During moderate exercise, a more gradual increase in ventilation occurs which causes an increase in carbon dioxide (C). This is because as muscles work, they produce carbon dioxide as a byproduct of metabolism. Hyperpnea, which is an increased rate and depth of ventilation, kicks in to meet the oxygen demand by the muscles and to expel the excess carbon dioxide. However, this hyperpnea starts due to neural mechanisms such as psychological stimuli, motor neuron activation, and activation of proprioceptors, and not necessarily due to a significant change in blood oxygen or carbon dioxide levels. These processes result in an increased breathing rate, helping to clear carbon dioxide and maintain pH levels. This adjustment allows the body to meet its physiological demand for oxygen during the period of exercise and is vital for maintaining homeostasis.