Final answer:
Pulmonary arterioles dilate in response to increased oxygen levels in the alveoli, optimizing perfusion to areas of the lungs with higher oxygen for efficient gas exchange.
Step-by-step explanation:
In ventilation-perfusion coupling, the pulmonary arterioles dilate under conditions of increased oxygen in the alveoli. This physiological response aims to optimize the blood flow (perfusion) to regions of the lungs with higher levels of oxygen, ensuring efficient gas exchange. When ventilation is high, providing a greater partial pressure of oxygen in the alveoli, it signals the pulmonary arterioles to expand, thus increasing perfusion to match the available oxygen. Conversely, when alveolar carbon dioxide levels are high, the bronchioles dilate to permit a more rapid expulsion of carbon dioxide. These adjustments contribute to maintaining a balanced ventilation/perfusion ratio (V/Q match), which is crucial for effective gas exchange.