What happens to your body when you get very cold? The physiological response to cold exposure

According to the National Institute for Occupational Safety and Health, cold stress can lead to serious injuries or death as the body works hard to maintain its core temperature. When you get very cold, your body initiates a complex series of physiological responses to conserve heat and protect vital organs, but these defenses can be overwhelmed, leading to severe health risks like hypothermia and frostbite.

Quick Summary

The body responds to very cold temperatures by diverting blood from the extremities to the core to protect vital organs, causing shivering and an increase in metabolic rate. This process, known as thermoregulation, is a critical survival mechanism, but if the core temperature drops too low, it can lead to dangerous conditions such as hypothermia, which affects brain function and motor skills.

Key Points

• Hypothalamus Control: Your brain's hypothalamus acts as a thermostat, triggering survival responses like shivering and vasoconstriction to maintain core temperature.

• Vasoconstriction: Blood vessels constrict in the skin and extremities to redirect warm blood to the core, which can cause frostbite in severe cases.

• Shivering: Involuntary muscle contractions generate heat to warm the body from within, but this process consumes energy rapidly and can lead to exhaustion.

• Hypothermia Dangers: If core temperature drops below 95°F, hypothermia sets in, affecting brain function and potentially leading to confusion, slurred speech, and death.

• Frostbite and Tissue Damage: Restricted blood flow to the extremities can cause tissues to freeze, leading to permanent damage and potential amputation.

• Cardiovascular Strain: Constricted blood vessels increase blood pressure, putting extra strain on the heart and increasing the risk of heart attack or stroke.

The Body's Initial Response to Cold

When your body is first exposed to cold, your brain's hypothalamus acts as a thermostat, triggering defenses to maintain core body temperature and protect vital organs [1, 2]. The primary responses are peripheral vasoconstriction and shivering [1, 2].

Peripheral Vasoconstriction

Peripheral vasoconstriction is the narrowing of blood vessels in areas like the skin and limbs, reducing blood flow to minimize heat loss through radiation, conduction, and convection [1]. While this helps keep the core warm, reduced blood flow to extremities can lead to cold-related injuries [1].

Shivering: An Involuntary Response

If vasoconstriction isn't enough, the hypothalamus triggers shivering, which is rapid, involuntary muscle contractions that generate heat [1]. Shivering is a vital survival mechanism, but it rapidly uses energy and can lead to exhaustion [1].

The Role of Hormones

Hormones like epinephrine and norepinephrine are released in response to severe cold, increasing metabolic rate and heat production, and contributing to vasoconstriction [1]. Thyroid hormones also play a role in boosting metabolism over time [1].

The Dangers of Prolonged Cold Exposure

If these initial defenses are insufficient, core body temperature drops, leading to more serious conditions like hypothermia and frostbite [1, 2].

Hypothermia

Hypothermia occurs when core body temperature falls below 95°F (35°C) and is a medical emergency [1]. Symptoms progress from shivering, fatigue, and confusion to slurred speech, memory loss, loss of coordination, and eventually, cessation of shivering, slowed heart rate and breathing, unconsciousness, and death [1]. Impaired brain function can lead to poor judgment, including paradoxical undressing [1].

Frostbite

Frostbite is caused by the freezing of skin and underlying tissues, often in extremities with restricted blood flow [1]. Early signs include numbness and pale or waxy skin [1]. Deeper frostbite can cause permanent tissue damage and potentially require amputation [1]. Affected areas should be gently rewarm

Frequently Asked Questions

What is the very first thing that happens when you get cold?

The very first physiological response is peripheral vasoconstriction, where blood vessels in your skin and extremities narrow. This reduces blood flow to those areas to conserve heat for your core organs.

Why do I shiver when I get very cold?

You shiver because your hypothalamus sends signals to your muscles to contract and relax rapidly. This involuntary action generates heat as a byproduct of the muscular movement, helping to raise your body's internal temperature.

What are the warning signs of hypothermia?

Early signs of hypothermia include uncontrollable shivering, exhaustion, confusion, and fumbling hands. As it progresses, symptoms can include slurred speech, drowsiness, memory loss, and a lack of coordination.

Can I get frostbite even if I'm not in freezing temperatures?

Yes, it is possible to get frostbite in cold temperatures above freezing, especially if there is wind chill or if your skin is wet. Wind can accelerate heat loss, and wet clothing loses its insulating properties, increasing your risk.

What is paradoxical undressing and why does it happen?

Paradoxical undressing is a phenomenon in severe hypothermia where a person becomes disoriented and feels intensely hot, leading them to remove their clothing. It is caused by the impaired function of the brain due to the dangerously low core temperature.

How does extreme cold affect people with heart conditions?

Extreme cold can be very dangerous for people with heart conditions. The constriction of blood vessels increases blood pressure and puts extra strain on the heart, raising the risk of heart attack or stroke. The cold can also thicken the blood, making it more prone to clotting.

Are older adults or children more vulnerable to cold weather?

Both older adults and young children are more vulnerable. Children lose heat faster due to a higher surface area to body mass ratio, while older adults may have a slower metabolism, less muscle mass, and underlying health conditions that affect temperature regulation.