Here’s the truth of it. Mother Earth, the blue planet, our very own 3rd rock from the sun is perfect for us. By that I mean this planet has more than enough places (from Bangkok to New Jersey) that are both warm and cool enough for us to survive and thrive as a species. Our solar system is a rough neighborhood. Even on the surface of the moon there is at least a 450° F difference between standing in the light and the shade. So believe me brothers and sisters when I say that it is truly remarkable that we get to hitch a ride on this cosmic trolley called Earth.
The human body has special needs. Our metabolism functions optimally within a narrow, warm fuzzy range between 36.5° C and 37.5° C (98-100° F). Most of us don’t climb much further than 98.6° F (hyperthermia) unless we’ve caught a nasty flu virus or overslept on a tanning bed. Now that is one tight range for homeostasis to be maintained. I’m talking tighter than a sumo wrestler in skinny jeans. This is the range where our enzymes can function optimally, where our cells can use energy stored in glucose, where blood can adequately deliver oxygen in exchange for carbon dioxide, and an [EXPLETIVE] load of other vital, biochemical gymnastics.
“Hypothermia” – is not an 80’s Hair Band
Medically speaking, hypothermia is the state at which your core body temperature drops below 35° C (95.0° F) but I’m willing to bet that for your core temperature to slide down even 3 degrees you’re already feeling pretty cold and have been for some time. If you put the lid on a warm cup of coffee and set it in the freezer you’d be lucky to find iced coffee waiting for you even a half hour later. The human body has water tight skin, fat tissue, body cavities, and many times the volume of a 16 oz cup of Joe. So when we get cold it’s the real thing and our body fights for us right up to the very end.
A word or two about Vasoconstriction
Consider that the blood flowing through our veins carries heat. So when we start to lose heat the blood becomes a kind of heat currency that the body gets mighty stingy with. So when the air gets frosty the blood will begin to move away from the small, surface vessels in the skin and concentrate its energy on the brain and other vital organs. The skin is also what is exposed to the cold air and where 90% of body’s heat is lost.
When it comes to survival by any means necessary my team captain will always be the hypothalamus. We actually have a shivering center of the brain located in the posterior hypothalamus, which is normally kept in check by the anterior portion of the hypothalamus. However, when the body’s core temperature drops just below it’s warm fuzzy range your posterior hypothalamus kicks in and says “everybody dance!” This leads to the short, rhythmic muscle contractions in an effort to generate heat.
So what happens when the big chill hits?
Stage 1 (mild – “Time to put the snow balls down and come inside”)
This occurs after a 1-2° drop in normal body temperature. Shivering, hypertension, tachycardia (heart rate over 100 rate/minute), and vasoconstriction (contriction of blood flow through vessels). Clinical cases vary in which hyperglycemia or hypoglycemia (high and low blood sugar) have occurred. The chances are roughly 50/50. As metabolism staggers the cells decrease their uptake of glucose and the tissue’s sensitivity to insulin becomes impaired allowing glucose to spill into the blood. This is a hyperglycemic state. However, having a low blood sugar to begin with (especially if you’ve been wandering around for hours in the cold) can accelerate the onset the onset of hypothermia.
Stage 2 (moderate – “Dude, you don’t look so good”)
This is seen after a 2-4° drop from normal. Ok we say moderate but by this point you’re pretty gosh dang cold and have been for some time. The surface vessels of the skin constrict, drawing blood to the vital organs, shivering, coordination, and mental state all worsen. Portions of the body rich in capillaries like fingers, toes, lips, ears (basically all the delicate parts most exposed to the air) all get pale and blue, and not in that sexy, Avatar kind of way.
Stage 3 (severe – “Somebody call an ambulance!”)
At this point the core temperature has dropped below 32° C and your body is pissed. The heart rate drops down to the 30s (normal resting heart rate for adults is at least 60 beats per minute), the respiratory rate decreases, the blood pressure drops. It’s like the temperature just turns your volume down. The vital organs are beginning to fail as metabolic functions stagger. Your muscle coordination and mental function are terrible by this point and you’d be lucky if you can unscrew the loose lid on a peanut butter jar or remember the words to “Happy Birthday.” Then something really, really strange tends to happen…
The Deadly Strip Tease
It’s a phenomenon referred to as paradoxical undressing. People at the edge of their sanity, in the most severe stages of hypothermia will begin taking off their clothes. They reach a state where they become hellah-confused, disoriented, and even violently aggressive where they just start shedding layers as if they were burning up. One theory is that by this point the body has been so beaten up that the signaling pathways of your hypothalamus are sending all the wrong messages like an evil cell phone that sends “let’s get back together” texts to all your ex’s. This is also associated with a “hide and die” syndrome (terminal burrowing). Victims are sometimes found curled up in small, hidden spaces. I don’t know physiology fans, perhaps in moments of extreme circumstance human beings simply switch back to our most primal selves.
So because I care here’s an ounce of prevention…
If you’re out in freezing temperatures stay dry (wet skin is a death sentence), wear multiple layers especially synthetic, poly blends that retain heat better then cotton, stay hydrated but avoid cold liquids that will just further lower your core temp, cover your head, and NO no no alcohol! It’s a vasodilator (increases blood flow in the vessels) drawing blood/heat to the extremities and thus away from your core. That rum n coke just isn’t worth it.
As always stay curious, stay classy, and never stop learning my friends 🙂