<written in 2018.12.29>
When you suddenly go into a pool of cold water, your breath becomes rapid. Same is when you are sprayed with cold water. This kind of reaction seems useless. But then, why does this happen?
This phenomenon is called a 'diving reflex'. Every species in the class Mammalia(mammals) have this reflex, occuring stronger in sea mammals than those living on the land. This diving reflex leads to some effects such as frequent and deep breathing, slower heartbeats, etc. Those are all survival instincts for mammals to stay alive longer in water.
When a mammal is covered by cold water, it's body concludes that it is about to drown, despite all other information. Not wanting to drown, the body tries to take in as much oxygen as possible. In order to do so, our lungs empty most of the CO2 in our body. This leads to hypocapnia(state of reduced carbon dioxide in the blood), hyperventilation(condition of breathing fast), and unbalance of oxygen and carbon dioxide levels, enabling the lungs to contain more oxygen than usual. The reduce of heartbeats is to decrease oxygen usage in the body. The diving reflex was a crucial instinct to survive for early mammals. It enabled them to survive longer underwater.
title image: https://www.openaccessgovernment.org/ocean-protection/77447/
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