What limits voluntary control over respiration?

Voluntary control over respiration is primarily influenced by the levels of carbon dioxide (CO2) and oxygen (O2) in the blood. The central chemoreceptors in the brainstem, particularly in the medulla oblongata, play a crucial role in monitoring the concentration of CO2, which is the primary driver for the respiratory rate and depth. An increase in CO2 levels triggers a strong respiratory response to help exhale excess CO2 and bring in more O2. This feedback mechanism often overrides voluntary control, especially during situations of high activity or stress when the body's demand for oxygen increases or when CO2 levels rise. Thus, while individuals can consciously control their breathing to a certain extent, when the metabolic demands change or CO2 levels become more critical, the involuntary responses take precedence, effectively limiting voluntary control over respiration.

Factors such as neurological damage or a diaphragm injury can also impact respiratory control, but the fundamental limit is rooted in the body's chemical regulation system based on blood gas levels. Similarly, environmental factors might affect breathing patterns or external conditions, but they do not intrinsically limit voluntary control like the physiological feedback from blood gases does.