Diving reflex

Diving reflex in a human baby

The diving reflex, also known as the diving response and mammalian diving reflex, is a set of physiological responses to immersion that overrides the basic homeostatic reflexes, and is found in all air-breathing vertebrates studied to date.[1][2][3] It optimizes respiration by preferentially distributing oxygen stores to the heart and brain, enabling submersion for an extended time.

The diving reflex is exhibited strongly in aquatic mammals, such as seals,[1][4] otters, dolphins,[5] and muskrats,[6] and exists as a lesser response in other animals, including human babies up to 6 months old (see infant swimming), and diving birds, such as ducks and penguins.[1] Adult humans generally exhibit a mild response, the dive-hunting Sama-Bajau people being a notable outlier.[7]

The diving reflex is triggered specifically by chilling and wetting the nostrils and face while breath-holding,[2][8][9] and is sustained via neural processing originating in the carotid chemoreceptors. The most noticeable effects are on the cardiovascular system, which displays peripheral vasoconstriction, slowed heart rate, redirection of blood to the vital organs to conserve oxygen, release of red blood cells stored in the spleen, and, in humans, heart rhythm irregularities.[2] Although aquatic animals have evolved profound physiological adaptations to conserve oxygen during submersion, the apnea and its duration, bradycardia, vasoconstriction, and redistribution of cardiac output occur also in terrestrial animals as a neural response, but the effects are more profound in natural divers.[1][3]

  1. ^ a b c d Butler PJ, Jones DR (1997). "Physiology of diving of birds and mammals" (PDF). Physiological Reviews. 77 (3): 837–99. doi:10.1152/physrev.1997.77.3.837. PMID 9234967.
  2. ^ a b c Cite error: The named reference Physiology and Pathophysiology was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference Panneton 2013 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference pmid2800051 was invoked but never defined (see the help page).
  5. ^ Noren SR, Kendall T, Cuccurullo V, Williams TM (2012). "The dive response redefined: Underwater behavior influences cardiac variability in freely diving dolphins". Journal of Experimental Biology. 215 (Pt 16): 2735–41. doi:10.1242/jeb.069583. PMID 22837445.
  6. ^ Cite error: The named reference McCulloch 2012 was invoked but never defined (see the help page).
  7. ^ Ilardo MA, Moltke I, Korneliussen TS, Cheng J, Stern AJ, Racimo F, de Barros Damgaard P, Sikora M, Seguin-Orlando A (April 2018). "Physiological and Genetic Adaptations to Diving in Sea Nomads". Cell. 173 (3): 569–580.e15. doi:10.1016/j.cell.2018.03.054. PMID 29677510.
  8. ^ Cite error: The named reference pmid636078 was invoked but never defined (see the help page).
  9. ^ Kinoshita T, Nagata S, Baba R, Kohmoto T, Iwagaki S (June 2006). "Cold-water face immersion per se elicits cardiac parasympathetic activity". Circulation Journal. 70 (6): 773–776. doi:10.1253/circj.70.773. ISSN 1346-9843. PMID 16723802.