What is a common response of the body to increased CO2 levels during strenuous activity?

• A. Increased heart rate
• B. Decreased respiratory rate
• C. Increased blood pressure
• D. Decreased metabolic activity

Answer: (A)

During strenuous activity, the body experiences an increase in carbon dioxide (CO2) levels due to heightened metabolic activity and oxygen consumption. In response to rising CO2 levels, one of the primary compensatory mechanisms is an increased heart rate. This response serves to enhance blood circulation, allowing for more efficient transport of oxygen to the tissues that are working hard and the removal of excess CO2 from the bloodstream.

The body's ability to sense changes in CO2 levels is crucial for maintaining homeostasis. Chemoreceptors detect elevated CO2 and, in turn, stimulate the cardiovascular system to elevate heart rate and increase cardiac output. This helps ensure that oxygen-rich blood reaches the muscles and vital organs quickly, supporting continued physical exertion.

Furthermore, the other answer choices indicate responses that are not typical during strenuous activity. For example, a decreased respiratory rate would hinder the body's ability to expel CO2, while an increase in blood pressure is typically a secondary response rather than a primary adjustment to CO2 levels. Decreased metabolic activity, on the other hand, is counterintuitive during strenuous exercise, as the body requires a heightened metabolic rate to meet energy demands.