Figure 4. Flow diagram illustrating the interaction between reflexes arising from inputs from arterial chemoreceptors, pulmonary stretch receptors, and nasopharyngeal receptors. When hypoxia occurs under conditions where respiratory activity can increase, the reflex decrease in heart rate and reflex increase in vascular resistance (in skeletal muscle and visceral beds) is opposed by the secondary reflex effects arising from activation of pulmonary stretch receptors, thus increasing oxygen uptake. In contrast, when hypoxia occurs under conditions when respiratory activity cannot increase, such as during submersion or exposure to a noxious substance in the ambient environment, the primary reflex response to chemoreceptor stimulation is reinforced by reflex effects arising from the nasopharyngeal reflex, leading to a greater degree of oxygen conservation.

From Dampney (2008), with permission.