On vigorous exercise, the respiratory function largely depends upon –
**Core Concept**
During vigorous exercise, the respiratory function is dramatically altered to meet the increased demand for oxygen and carbon dioxide removal. The body's need for oxygen increases to meet the energy requirements of the muscles, and carbon dioxide production rises as a result of anaerobic metabolism.
**Why the Correct Answer is Right**
The correct answer is that respiratory function largely depends upon the **ventilatory reserve**, which is the ability of the lungs to increase ventilation in response to increased metabolic demands. This is mediated by the **chemoreceptors** in the carotid bodies and aortic bodies, which detect changes in blood pH, pCO2, and pO2 levels. The ventilatory response is also influenced by the **Hering-Breuer inflation reflex**, which limits lung inflation and prevents excessive ventilation.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not accurately describe the primary mechanism by which respiratory function is altered during vigorous exercise.
* **Option B:** This option is incorrect because it is not a relevant factor in the regulation of respiratory function during exercise.
* **Option C:** This option is incorrect because it is not a primary mechanism by which respiratory function is altered during vigorous exercise.
**Clinical Pearl / High-Yield Fact**
The Hering-Breuer inflation reflex is an important mechanism that helps prevent overinflation of the lungs during exercise, but it can be overridden by strong inspiratory efforts.
**Correct Answer: D. Ventilatory reserve**