The Mammalian Diving Response: An Enigmatic Reflex to Preserve Life?

The mammalian diving response is a remarkable behavior that overrides basic homeostatic reflexes. It is most studied in large aquatic mammals but is seen in all vertebrates. Pelagic mammals have developed several physiological adaptations to conserve intrinsic oxygen stores, but the apnea, bradycardia, and vasoconstriction is shared with those terrestrial and is neurally mediated. The adaptations of aquatic mammals are reviewed here as well as the neural control of cardiorespiratory physiology during diving in rodents.

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Visualizing metabolic transitions in aquatic mammals: does apnea plus swimming equal "diving"?

Canadian Journal of Zoology ◽

10.1139/z88-005 ◽

1988 ◽

Vol 66 (1) ◽

pp. 40-44 ◽

Cited By ~ 7

Author(s):

Michael A. Castellini

Keyword(s):

Marked Change ◽

Plasma Metabolites ◽

Diving Response ◽

Oxygen Utilization ◽

Metabolic Plasticity ◽

Long Duration ◽

Metabolic Conditions ◽

Metabolic Variation ◽

The One ◽

Aquatic Mammals

While diving, aquatic mammals must balance the oxygen conservation requirements of apnea with the oxygen utilization requirements of exercise. The resulting metabolic state depends on a complex range of behavioral, physiological, and metabolic conditions as required by the particular dive profile. Thus, at the one extreme of long duration diving, oxygen conservation requirements will outweigh those of exercise, while under conditions of rapid, short diving or propoising, exercise parameters will probably be of more importance than those of oxygen conservation. In the last several years, techniques for monitoring radioactively tagged plasma metabolites have allowed the visualization of metabolic variation throughout various diving and surface exercise regimes in aquatic mammals. By comparing such tracer turnover dilution curves under conditions of surface exercise, quiet forced diving, free diving, and sleep apnea, patterns emerge that demonstrate the extreme metabolic plasticity of the diving response. These comparisons have led to the conclusions that even short diving periods probably involve a marked change in metabolic steady state, and that aerobic diving is not simply analogous to aerobic exercise.

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Respiratory and cardiovascular control during diving in birds and mammals.

Journal of Experimental Biology ◽

10.1242/jeb.100.1.195 ◽

1982 ◽

Vol 100 (1) ◽

pp. 195-221 ◽

Cited By ~ 4

Author(s):

P J Butler

Keyword(s):

Small Animals ◽

Diving Response ◽

Alarm Response ◽

Marine Birds ◽

Safety Mechanism ◽

Exercise Response ◽

Oxygen Stores ◽

Underwater Exploration ◽

The Brain ◽

Classical Hypothesis

Recent studies on freely diving birds and mammals indicate that, contrary to the classical hypothesis, the majority of dives are aerobic with minimal cardiovascular adjustments (i.e. bradycardia and selective vasoconstriction). It is postulated that during these aerobic dives the cardiovascular adjustments result from the opposing influences of exercise and the classical diving response, with the bias towards the exercise response. It is envisaged that the active muscles, as well as the brain and heart, are adequately supplied with blood to enable them to metabolize aerobically. Intense mental activity, particularly in carnivores seeking their prey, may also attenuate the classical response. Aerobic dives are usually terminated well before the oxygen stores are depleted, and another dive follows once they have been replenished. In this way a series of dives is performed. Prolonged dives are endured as a result of a shift towards the classical response of bradycardia, presumably more intense vasoconstriction, and anaerobiosis. This may be a form of alarm response, particularly in small animals such as ducks and coypus, or it may be a means of allowing the marine birds and mammals that dive deeply for their food to engage in unusually long hunting expeditions. For those that dive under ice, it may also allow long periods of underwater exploration as well as being a safety mechanism should the animal become disoriented.

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Breath-hold diving as a brain survival response

Translational Neuroscience ◽

10.2478/s13380-013-0130-5 ◽

2013 ◽

Vol 4 (3) ◽

Cited By ~ 6

Author(s):

Zeljko Dujic ◽

Toni Breskovic ◽

Darija Bakovic

Keyword(s):

Blood Flow ◽

Cardiac Output ◽

Respiratory Muscles ◽

Breath Hold ◽

Diving Response ◽

Compensatory Mechanisms ◽

Physiological Adaptations ◽

O2 Delivery ◽

World Records ◽

The Brain

AbstractElite breath-hold divers are unique athletes challenged with compression induced by hydrostatic pressure and extreme hypoxia/hypercapnia during maximal field dives. The current world records for men are 214 meters for depth (Herbert Nitsch, No-Limits Apnea discipline), 11:35 minutes for duration (Stephane Mifsud, Static Apnea discipline), and 281 meters for distance (Goran Čolak, Dynamic Apnea with Fins discipline). The major physiological adaptations that allow breath-hold divers to achieve such depths and duration are called the “diving response” that is comprised of peripheral vasoconstriction and increased blood pressure, bradycardia, decreased cardiac output, increased cerebral and myocardial blood flow, splenic contraction, and preserved O2 delivery to the brain and heart. This complex of physiological adaptations is not unique to humans, but can be found in all diving mammals. Despite these profound physiological adaptations, divers may frequently show hypoxic loss of consciousness. The breath-hold starts with an easy-going phase in which respiratory muscles are inactive, whereas during the second so-called “struggle” phase, involuntary breathing movements start. These contractions increase cerebral blood flow by facilitating left stroke volume, cardiac output, and arterial pressure. The analysis of the compensatory mechanisms involved in maximal breath-holds can improve brain survival during conditions involving profound brain hypoperfusion and deoxygenation.

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The rat: a laboratory model for studies of the diving response

Journal of Applied Physiology ◽

10.1152/japplphysiol.00600.2009 ◽

2010 ◽

Vol 108 (4) ◽

pp. 811-820 ◽

Cited By ~ 32

Author(s):

W. Michael Panneton ◽

Qi Gan ◽

Rajko Juric

Keyword(s):

Marine Mammals ◽

Neural Control ◽

Diving Behavior ◽

Laboratory Model ◽

Diving Response ◽

Hemodynamic Variables ◽

Autonomic Reflex ◽

The Brain ◽

Brain Study ◽

Stimulation Of

Underwater submersion in mammals induces apnea, parasympathetically mediated bradycardia, and sympathetically mediated peripheral vasoconstriction. These effects are collectively termed the diving response, potentially the most powerful autonomic reflex known. Although these physiological responses are directed by neurons in the brain, study of neural control of the diving response has been hampered since 1) it is difficult to study the brains of animals while they are underwater, 2) feral marine mammals are usually large and have brains of variable size, and 3) there are but few references on the brains of naturally diving species. Similar responses are elicited in anesthetized rodents after stimulation of their nasal mucosa, but this nasopharyngeal reflex has not been compared directly with natural diving behavior in the rat. In the present study, we compared hemodynamic responses elicited in awake rats during volitional underwater submersion with those of rats swimming on the water's surface, rats involuntarily submerged, and rats either anesthetized or decerebrate and stimulated nasally with ammonia vapors. We show that the hemodynamic changes to voluntary diving in the rat are similar to those of naturally diving marine mammals. We also show that the responses of voluntary diving rats are 1) significantly different from those seen during swimming, 2) generally similar to those elicited in trained rats involuntarily “dunked” underwater, and 3) generally different from those seen from dunking naive rats underwater. Nasal stimulation of anesthetized rats differed most from the hemodynamic variables of rats trained to dive voluntarily. We propose that the rat trained to dive underwater is an excellent laboratory model to study neural control of the mammalian diving response, and also suggest that some investigations may be done with nasal stimulation of decerebrate preparations to decipher such control.

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The Mammalian Diving Response: Inroads to Its Neural Control

Frontiers in Neuroscience ◽

10.3389/fnins.2020.00524 ◽

2020 ◽

Vol 14 ◽

Author(s):

W. Michael Panneton ◽

Qi Gan

Keyword(s):

Neural Control ◽

Diving Response

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Cardiovascular and respiratory responses to apneas with and without face immersion in exercising humans

Journal of Applied Physiology ◽

10.1152/japplphysiol.01057.2002 ◽

2004 ◽

Vol 96 (3) ◽

pp. 1005-1010 ◽

Cited By ~ 67

Author(s):

Johan P. A. Andersson ◽

Mats H. Linér ◽

Anne Fredsted ◽

Erika K. A. Schagatay

Keyword(s):

Oxygen Uptake ◽

Anaerobic Metabolism ◽

Lactate Concentration ◽

Cardiovascular Responses ◽

Cycle Ergometer ◽

Diving Response ◽

Face Immersion ◽

Oxygen Stores ◽

Plasma Lactate Concentration ◽

Alveolar Gas Exchange

The effect of the diving response on alveolar gas exchange was investigated in 15 subjects. During steady-state exercise (80 W) on a cycle ergometer, the subjects performed 40-s apneas in air and 40-s apneas with face immersion in cold (10°C) water. Heart rate decreased and blood pressure increased during apneas, and the responses were augmented by face immersion. Oxygen uptake from the lungs decreased during apnea in air (-22% compared with eupneic control) and was further reduced during apnea with face immersion (-25% compared with eupneic control). The plasma lactate concentration increased from control (11%) after apnea in air and even more after apnea with face immersion (20%), suggesting an increased anaerobic metabolism during apneas. The lung oxygen store was depleted more slowly during apnea with face immersion because of the augmented diving response, probably including a decrease in cardiac output. Venous oxygen stores were probably reduced by the cardiovascular responses. The turnover times of these gas stores would have been prolonged, reducing their effect on the oxygen uptake in the lungs. Thus the human diving response has an oxygen-conserving effect.

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