Question

question 17
1 pts
which of the following would you expect to happen to cellular respiration during exercise?
increased cellular respiration occurs during exercise, causing a rise in plasma pco2, which is detected by central chemoreceptors in the brain and perhaps peripheral chemoreceptors in the carotid sinus and aorta to cause an increase in respiration rate.
decreased cellular respiration occurs during exercise, causing a rise in plasma pco2, which is detected by central chemoreceptors in the brain and perhaps peripheral chemoreceptors in the carotid sinus and aorta to cause a decrease in respiration rate.
exercise causes a decrease in cellular respiration by shifting peripheral chemoreceptors in the heart to cause retention of oxygen.
increased cellular respiration occurs during exercise, causing a decrease in plasma pco2, which is detected by central chemoreceptors in the brain and perhaps peripheral chemoreceptors in the carotid sinus and aorta to cause a decrease in respiration rate.
question 18
1 pts
the pco₂ in alveolar air is _____ blood.
less than in the systemic venous
greater than in the systemic venous
equal to the systemic arterial
both a and c are correct.

Explanation:

• Question 17: During exercise, muscle activity increases, so cellular respiration (which produces ATP for muscle contraction) increases. More cellular respiration means more \(CO_2\) is produced (since \(CO_2\) is a by - product of aerobic respiration). The rise in plasma \(PCO_2\) (partial pressure of carbon dioxide) is detected by chemoreceptors (central in the brainstem and peripheral in the carotid sinus and aorta). This detection leads to an increase in the respiration rate (to expel the excess \(CO_2\)).
• Question 18: Systemic venous blood has a high \(PCO_2\) (around 45 mmHg) because it has collected \(CO_2\) from the tissues. Alveolar air has a \(PCO_2\) of about 40 mmHg. Systemic arterial blood, which has been oxygenated and had \(CO_2\) removed in the lungs, also has a \(PCO_2\) of about 40 mmHg. So, alveolar \(PCO_2\) is less than in systemic venous blood (A is correct) and equal to systemic arterial blood (C is correct).

Answer:

• Question 17: Increased cellular respiration occurs during exercise, causing a rise in plasma \(PCO2\), which is detected by central chemoreceptors in the brain and perhaps peripheral chemoreceptors in the carotid sinus and aorta to cause an increase in respiration rate.
• Question 18: Both A and C are correct.