Final answer:
The high partial pressure of O2 in the alveolus causes the pulmonary arterioles to dilate and increases blood flow, ensuring optimal gas exchange by directing blood toward well-ventilated alveoli.
Step-by-step explanation:
When there is dead space in the alveolus, resulting in a high partial pressure of O2, it triggers the pulmonary arterioles to dilate. The dilation of pulmonary arterioles leads to an increase in blood flow to the well-ventilated alveoli. Therefore, the correct answer is a) Dilate, increase. This mechanism ensures that areas of the lung which are well ventilated and have a higher oxygen content can receive more blood, thereby optimizing the gas exchange process.
In contrast, when ventilation is not adequate and the partial pressure of oxygen in the alveoli drops, the pulmonary arterioles serving those alveoli constrict, redirecting blood to better-ventilated areas. Adjustments in blood vessel diameter are a crucial aspect of the body's response to varying levels of oxygen and carbon dioxide in the lungs and help maintain efficient gas exchange.
the correct answer is a) Dilate, increase