Final answer:
When there is dead space in the alveolus, the low partial pressure of CO2 will cause smooth muscles to constrict the airway, reducing airflow. This is because the diameter of the bronchioles is sensitive to the partial pressure of carbon dioxide, and increased CO2 levels result in bronchiole constriction.
Step-by-step explanation:
When there is dead space in the alveolus, the low partial pressure of CO2 will act on smooth muscles to constrict the airway which will decrease air flow. The diameter of the bronchioles is sensitive to the partial pressure of carbon dioxide in the alveoli. A greater partial pressure of carbon dioxide causes the bronchioles to constrict, reducing the diameter of the airway and decreasing the flow of air. This is because a lower level of CO2 in the alveoli indicates sufficient gas exchange, so there is no need for excessive airflow.
Ventilation is regulated by the diameter of the airways, whereas perfusion is regulated by the diameter of the blood vessels. The diameter of the bronchioles is sensitive to the partial pressure of carbon dioxide in the alveoli. A greater partial pressure of carbon dioxide in the alveoli causes the bronchioles to increase their diameter as will a decreased level of oxygen in the blood supply, allowing carbon dioxide to be exhaled from the body at a greater rate. As mentioned above, a greater partial pressure of oxygen in the alveoli causes the pulmonary arterioles to dilate, increasing blood flow.