Cold: what happens in our body during hypothermia?

How does our body react when we are exposed to freezing temperatures? Pieter Vancamp, post-doctoral biologist at the Catholic University of Louvain, answers this question in a new article by The Conversation. “Fortunately, we are not entirely helpless in the face of the cold. Our body functions optimally at a given temperature, but has techniques for heating up and limiting losses”, explains the biologist. Indeed, our ideal body temperature is around 36.6°C: this is the level at which cells develop best.

“The control center for our body temperature is found in the hypothalamus, a small region located at the base of the brain. Working like an extremely precise thermostat, it reacts to information received via ultra-sensitive sensors located in the skin, spinal cord , the abdomen and the great veins”continues Pieter Vacamp.

How does the maintenance of internal body heat work?

As the biologist develops, at the slightest deviation from 36.6°C, the body pushes our internal boiler. In this case, it increases our heat production and reduces energy loss thanks to involuntary mechanisms known to all: “piloerection” (our hair, or what is left of it, straightens to enlarge our layer of insulating air), shivering (our muscles contract to increase metabolism up to five times and generate more heat) and the redirection of warm blood away from cold external surfaces; hence our pale skin. So, even if your toes and fingers are cold when you walk in the snow, your central organs continue to benefit from the famous 36.6°C. Physiologists call this ability to keep our internal temperature constant, regardless of external conditions, “homeostasis”.

But that’s not all: the cold also leads to behavioral responses. Besides our body, the hypothalamus also informs the higher regions of the brain of the situation, managing logic and the search for solutions. It’s what drives us to look for warmer places, to shelter from the wind, to drink something warm…

2°C less is enough to deeply affect the body

“But our ability to resist the cold has its limits (clothing too light or wet in freezing weather, staying outside in the cold for too long, an interior that is too cool, etc.). When these are exceeded, the inside of the body begins to cool down. We talk about hypothermia when our core temperature drops below 35°C.”adds Pieter Vacamp.

Two degrees lower than our normal internal temperature is enough to reduce the activity of our proteins and cause the metabolism of our cells to drop to levels so low that they threaten the functioning of vital organs. “It’s as if the engine of the body starts to sputter”notes Pieter.

Hypothermia: the signs are not just physical

The biologist details the multiple physical effects of hypothermia: our heart pump beats slower and weaker, which leads to a weak pulse. Rapid movement and movement can even cause irregular heartbeats. And at the same time, blood clotting decreases. Our metabolism, reduced, weakens the muscles of the lungs. Our breathing (inspiration and expiration) is slower, more superficial. Chills appear at first, but as our mitochondria become less efficient, the energy supply weakens. After a certain stage, a severely undercooled person no longer shivers, which is a serious warning sign.

Moreover, our spirit is not spared either. The best indicators of hypothermia could be changes in behavior: people in a state of hypothermia become confused, do not realize that they are cold (because it happens gradually), talk more and more hard and act weird. “If these signals are not taken into account in time, the situation can quickly endanger our lives”warns the biologist.