Respiratory Chemoreception Across Internal States.

The respiratory chemoreflexes help maintain arterial PCO2 and PO2 within a narrow range by adjusting lung ventilation. In any given moment, the sensitivity of the respiratory chemoreflexes to PCO2 and PO2 is influenced by internal state, a term that refers to how the brain processes incoming information. This review examines how interactions between neural mechanisms underpinning the respiratory chemoreflexes and internal state account for the respiratory response to exercise, acute psychological stress, pregnancy, and the sensation of air hunger. Together, these examples highlight internal state as a key determinant of homeostatic respiratory motor output and emphasize that the respiratory effects of hypercapnia and hypoxia cannot be understood independently of the state in which they occur.