Fig. 1.

Schematic of closed-loop respiratory control model including neural, mechanical, and chemosensory components. Bursting oscillations of the brain stem CPG membrane potential (V) activate motor neurons (α) to cause increases in lung volume (vol_L) and inspiration. Inhaled air increases alveolar oxygen partial pressure ($P{A}_{O_2}$). Oxygen enters the bloodstream through gas exchange. Arterial oxygen partial pressure ($P{a}_O{}_{{}_2}$) is monitored by chemoreceptors that regulate input drive current (I_tonic) to the CPG by modulating excitatory synaptic conductances (g_tonic). This respiratory control circuit can maintain $P{A}_{O_2}$ levels in the desired range around 100 mmHg.