Final answer:
The main stimulus for increasing pulmonary ventilation during exercise is the increase in blood concentration of carbon dioxide and the neural input from proprioceptors.
Step-by-step explanation:
The main stimulus for increasing pulmonary ventilation during exercise is the increase in blood concentration of carbon dioxide (CO2). When we exercise, our muscle cells produce more CO2 as a byproduct of cellular respiration. CO2 is then transported in the blood to the respiratory centers in the brain, which respond by increasing the rate and depth of ventilation to remove the excess CO2 and provide more oxygen to the working muscles.
Additionally, exercise also stimulates proprioceptors in the muscles, joints and tendons, which create a neural stimulus that triggers the respiratory centers in the brain to increase ventilation.
Therefore, the main stimulus for increasing pulmonary ventilation during exercise is the increase in blood concentration of carbon dioxide and the neural input from proprioceptors.