Which of the following occurs when cardiac output rises? A) The amount of O₂diffusing from alveolar air into the blood decreases. B) The amount of blood flowing to the lungs increases. C) The amount of O₂ consumed by muscles decreases. D) The surface area available for O₂ diffusion decreases. E) The amount of CO₂ retained by the lungs increases.

Question

Quizplus · Accepted Answer

When cardiac output increases, more blood is pumped by the heart per unit time. This means that the amount of blood flowing to the lungs also increases, which can improve the efficiency of gas exchange in the lungs. Option A is incorrect because an increase in cardiac output should not directly affect the diffusion of oxygen (O₂) from alveolar air into the blood. Option C is incorrect because an increase in cardiac output may actually lead to greater oxygen consumption by muscles, as more oxygenated blood is delivered to them. Option D is incorrect because an increase in cardiac output should not reduce the surface area available for gas exchange in the lungs. Option E is incorrect because an increase in cardiac output should not lead to an increase in carbon monoxide (CO₂) retention by the lungs.

Which of the Following Occurs When Cardiac Output Rises