Physiology, Diving Reflex

The diving reflex, commonly referred to as the mammalian dive reflex, diving bradycardia, and the diving response, is a protective, multifaceted physiologic reaction that occurs in mammals, including humans, in response to water submersion. Aspects of the dive reflex were first described in 1786 by Edmund Goodwyn; however, it would take until an 1870 publication by Paul Bert for the physiologic adaptations to be recognized. The dive reflex is believed to aid in conserving mammal oxygen stores by initiating several specific physiologic changes during aquatic immersion. When a human holds their breath and submerges in water, the face and nose become wet, which in turn causes bradycardia, apnea, and increased peripheral vascular resistance; these three main physiologic changes are collectively referred to as the diving reflex. The cause of increased peripheral resistance is thought to redistribute blood to the vital organs while limiting oxygen consumption by nonessential muscle groups. In addition to vascular resistance, bradycardia is initiated to decrease the work of the heart and further limit unnecessary oxygen consumption. The dive reflex is an innate multi-system physiologic response in all vertebrates that preserves oxygen stores during water immersion.