FIG. 18:  The simultaneous sympathetic and vagal activation in response to apnea see in the previous Figure constitutes part of the “diving reflex,” shown in this Figure from a healthy young subject who is wide awake.^[7]  He holds his breath for about 30 seconds, the hypoxemia stimulates the peripheral chemoreceptors, causing an increase in sympathetic drive together with a vagal cardiac activation resulting in bradycardia, and the result is a P-wave with no QRS, thus indicating complete heart block.  This is an example of the “diving reflex” during apnea, which elicits significant autonomic responses, namely sympathetic activation and vagal activation.