When your body is exposed to cold temperatures, it will automatically trigger a series of physiological responses in an attempt to preserve heat and maintain your core body temperature. The intensity of these responses depends on how cold you are and how long you have been exposed to the cold.
Shivering
One of the first things your body will do when you get too cold is shiver. Shivering is an involuntary contraction of your muscles that helps generate heat by expending energy. Small muscles around your vital organs will start to contract and relax rapidly, creating warmth through this muscle activity. Shivering can raise your overall metabolism by up to 5 times the normal rate, allowing more heat production.
Blood Vessel Constriction
As your body cools, your blood vessels will start to constrict, particularly in your extremities like your fingers, toes, ears, and nose. This reduces blood flow to your skin and extremities, limiting heat loss from your circulatory system to retain more warmth in your core. Blood vessel constriction decreases the surface area through which you lose heat.
Piloerection
You may also experience piloerection when you get cold. This is what causes goosebumps and is technically the contraction of small muscles connected to hair follicles in your skin. Piloerection causes your hairs to stand up, which helps trap an insulating layer of warm air around your body. The raised hairs also minimize heat loss by decreasing air circulation near the surface of your skin.
Increased Metabolic Rate
In addition to shivering, your body’s core metabolic rate will increase slightly when exposed to the cold. Your thyroid and adrenal glands secrete hormones like epinephrine and norepinephrine that boost your metabolism, increasing the number of calories you burn and the amount of heat you produce.
Curling Up
You may find yourself curling up or hunching your shoulders when feeling cold. This conserves body heat by minimizing the amount of skin surface area exposed to the external cold air. Curling up helps retain warmth around your vital organs.
Seeking Warmth
On a subconscious level, your body will seek out warmth when it is cold. You may find yourself moving into the sunlight, sitting by a heater, or cuddling with another warm body. Seeking warmth helps return your body temperature to normal.
Decreased Blood Flow to Extremities
In addition to constricting blood vessels, your body will preserve core warmth by reducing blood circulation to your extremities like your fingers, toes, nose, and ears. Less blood flows to these peripheral body parts so more stays warm around your critical internal organs.
Increased Heat Production
Your hypothalamus, the temperature control center in your brain, will kick into overdrive when you get cold. It stimulates mechanisms that generate more body heat through increased metabolism, shivering, and burning fat stores for fuel. You’ll produce more internal warmth to counteract the cold.
Suppressed Immune System
Studies show that being exposed to cold temperatures suppresses your immune system temporarily. Your body conserves its energy and resources for heating and defending your core rather than fighting infections when faced with cold stress.
Urination Decreases
You’ll also notice you urinate less when you’re cold. This is due to vasoconstriction and your body attempting to preserve fluid volume to maintain blood pressure. Less urination helps your body retain heat that would otherwise be lost when excreting warm fluids.
| Response | Mechanism |
|---|---|
| Shivering | Muscle contractions generate heat through motion |
| Blood vessel constriction | Constricts blood vessels to decrease heat loss |
| Piloerection (goosebumps) | Hairs stand up to trap warm air layer around skin |
| Increased metabolic rate | Burns more calories to increase body heat production |
| Curling up | Minimizes exposed surface area to retain body heat |
| Seeking warmth | Behavioral response to return body temperature to normal |
| Decreased blood flow to extremities | Reduces blood circulation to peripheral regions to conserve core heat |
| Increased heat production | Metabolic and hormonal mechanisms generate more internal warmth |
| Suppressed immune system | Conserves energy for heating instead of fighting infections |
| Decreased urination | Retains fluid volume and preserves heat lost through urine output |
Preventing Hypothermia
All of these physiological responses serve to defend your core temperature when you get cold. However, prolonged or extreme cold exposure can overwhelm your body’s capacity to produce enough heat. This puts you at risk of hypothermia, a dangerous lowering of your internal body temperature.
Hypothermia occurs when your core body temperature drops below 95°F (35°C). It impairs your brain and nervous system function and can be fatal if left untreated. Seniors, babies, and people who are exhausted or intoxicated are most susceptible.
You can prevent hypothermia by dressing appropriately for cold weather. Wear warm layers and protective garments like hats, gloves, and waterproof shoes. Keep your head, neck, hands, and feet covered since you lose the most heat from these areas.
Other tips to avoid hypothermia include staying dry, avoiding getting chilled to the bone, eating enough calories to fuel your metabolism, and seeking shelter to get out of the cold. If your body heat drops dangerously low, get medical assistance immediately.
Adaptation to Cold Exposure
When you’re regularly exposed to colder environments, your body can physiologically adapt to become more resilient against cold stresses. People who live in cold climates develop improved adaptive responses.
For example, repeated cold exposure leads to insulating fat deposits around vital organs and thicker subcutaneous fat. Your blood volume increases to deliver more warmth to the skin. You produce more metabolites to ramp up heat generation.
Cold-adapted people also have vasodilation reflexes that allow better blood circulation in the cold. Their average metabolic rate adjusts so they burn more calories for body heat production.
Seasonal Physiological Changes
Your body will even respond and adapt to seasonal drops in temperature. In the winter, your thyroid activity increases to boost metabolism. You may notice increased appetite and cravings for higher calorie foods.
Of course, these cold-adaptive responses vary based on factors like your age, fitness level, health status, and how abruptly the temperature changes. But in general, your body works hard to maintain thermal equilibrium when you get too cold.
Conclusion
Your body has an intricate physiological system designed to preserve your core temperature and protect against cold stresses. When exposed to cold, you’ll involuntarily shiver, get goosebumps, feel your extremities numb, curl up to conserve heat, and seek warmth. Your blood vessels constrict while your metabolism ramps up to generate more internal body heat. These automatic reactions help ensure your thermal homeostasis in the face of declining external temperatures.