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Diving response
Science Background
BIOLOGY
Human
Physiology
Diving response
The diving response is a reflex in mammals, which optimizes respiration to allow staying
underwater for extended periods of time. The reflex is stronger for aquatic mammals but
also exists in other mammals, including humans. Especially in babies up to six months old.
The diving response is triggered by cold water contacting the face.
Physiological effects
Upon initiation of the reflex three physiological effect scan be found in the body. The first
response to submerging is the slowing down of the heart (10-25%). The heart rate of
aquatic mammals slows down even more dramatic. Slowing the heart rate lessens the
need for bloodstream oxygen, leaving more to be used in the other organs.
Under high pressure capillaries in the extremities start closing off. First in the toes and
fingers, then hands and feet, allowing more blood to flow to the heart and brain.
In human about 12% of the total oxygen provision is stored in the muscles.
However, in mammals living in aquatic environments, it can be up to 30%, making the
muscles remain active for a long time in spite of the fact that the blood flow has been
closed. Finally, the blood will shift more towards the vital organs, particularly the lungs.
The reflex starts when receptors in the face, that are sensitive to cold, are triggered. Via
the cranial nerve the information is transported to the brains after which the autonomic
nervous system is activated. As a result, the heart rate is lowered, and the blood is nog
longer pumped to the extremities.
By means of a cranial nerve, the information is relayed to the brains after which the
autonomic nervous system is activated. As a result, the heart rate is lowered, and the
blood is no longer pumped to the extremities.
In humans, the reflex does not take place when only the legs or arms are submerged in
cold water. A lighter reflex can be observed when a test subject only holds his/her breath
without being in contact with cold water. The reflex is strengthened when the face is
submerged in cold water and the breathing is continued. The reflex becomes stronger as
the water temperature decreases. The reflexes are the strongest when the test person
holds his/her breath and submerge the face in the same time.
Source: The human diving response in a functional and comparative perspective, Erika
Schagatay
Diving Response – Science Background
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