However, when pushed these mechanisms can fail leading to an extreme breakdown.

So, what actually happens to your body and brain when you freeze to death? Hypothermia occurs

when the core body temperature drops below 37 degrees Celsius,

so in the event that the body is exposed to extreme cold, within minutes signals are sent from the skin to the hypothalamus

producing what is known as the Thermoeffector

Response. First, the blood vessels in our skin narrow,

allowing the body to maintain its core temperature by reducing the blood flow on its surface, known as Vasoconstriction. Additionally, brown adipose tissue,

located throughout the body, also activates using high levels of glucose and lipids to produce heat via a process called Nonshivering

Thermogenesis.

But, if all else fails our body undergoes Shivering Thermogenesis as a last-ditch effort

By constantly contracting our skeletal muscles, our body induces shivering in an attempt to produce enough heat to prevent hypothermia.

However, if you remain exposed to the cold, within 30 minutes

you could get frostbite, which is when your skin and other tissues literally begin to freeze.

Developing ice crystals endanger your cells by damaging their cell membranes, causing Intracellular

Dehydration, due to water leaking out from them. The cells then begin to die and the ice crystals continue to expand,

damaging neighboring cells. In response, the body tries to prevent frostbite in our skin through Vasodilation,

which allows increased blood flow to warm the skin cells.

However,

this runs counter to the Thermoeffector Response, which again works to maintain our core temperature through

Vasoconstriction. As a result, our body goes through cycles of Vasodilation and

Vasoconstriction, thawing and freezing our skin over and over again and causing even more damage.

But, our skin isn't the only spot that will freeze under extreme cold temperatures. If you're in extreme cold, windy weather your

corneas can freeze too, the protective layer of tears covering the cornea can dry,

making your eyes sensitive to light and causing eyelid spasms.

Luckily, your corneas can thaw if you get yourself out of the cold quickly,

but if frozen long enough,

you can cause permanent damage. Now, several factors, including body composition,

clothing, temperature, and the environment determine how quickly your core body temperature drops.

For example, heat is lost much more quickly in water than in air.

Those who were submerged in the icy waters after the sinking of the Titanic may have lasted only 15 minutes,

this is because during the advanced stage of hypothermia your organs begin to fail,

your breathing rate slows, you lose coordination, your heart rate begins to slow down, and your body even stops shivering.

One of the last symptoms of advanced stage hypothermia is delirium, a survey of cases in which death was caused by hypothermia found that in

25% of the cases,

the victims had undressed before they died. In one case, victims had neatly folded their clothes beside them and froze to death in the snow.

Why would this happen? One theory

is that the brain damage that results from the extreme cold

causes people to think that they're burning up, so they strip naked and cool down. Another theory suggests that the muscles that cause Cutaneous

Vasoconstriction in our blood vessels get exhausted and cause blood from our core to rush to the surface of our body,

resulting in a hot flash. This is all pretty bleak,

but if you find someone who appears to be frozen to death, you may want to warm them up. An aptly named paper,

No One is Dead Until Warm and Dead, chronicles a patient with hypothermia caused by drowning with no signs of life.

This patient was successfully resuscitated with a 3-hour bypass surgery used to warm his body. Though parts of his body required

amputation, in 11 weeks he successfully recovered with normal neurological function.

Just remember, when the temperature starts to drop,

do everything you can to stay warm, because your body can only do so much to fight the extreme cold.

So what are the techniques to help your body survive freezing to death? We made a video of step-by-step

strategies to stay alive if you're ever trapped in the extreme cold. Click here to learn the life-saving,

but also gruesome things you need to know to avoid hypothermia and

freezing to death. With climate change causing extreme weather, we may all need this info in the future, and subscribe for more weekly science videos.