What happens when we are too cold?

As a specialist in the field of human physiology, I can provide a detailed explanation of what happens to the human body when it becomes too cold. The body has a sophisticated system for maintaining a stable internal temperature, known as homeostasis. When the body detects that it is too cold, it initiates a series of physiological responses to counteract the drop in temperature and preserve its core temperature.

Step 1: Initial Response - Shivering
The first response to cold is often shivering. This is an involuntary contraction of muscles that generates heat as a byproduct. Shivering can increase the body's heat production by up to 400-500%, which is a significant increase and can help to raise the body's temperature.

Step 2: Vasoconstriction
Another response to cold is vasoconstriction, the narrowing of blood vessels, particularly those near the skin's surface. This reduces blood flow to the skin and extremities, which in turn reduces heat loss from the body. By conserving heat in this way, the body can maintain its core temperature more effectively.

Step 3: Peripheral Insulation
In addition to vasoconstriction, the body may also reduce heat loss by increasing peripheral insulation. This can involve behaviors such as putting on more clothing, seeking shelter, or even huddling with others for warmth.

Step 4: Non-Shivering Thermogenesis
The body also has a process called non-shivering thermogenesis, which is a heat-producing process that does not involve shivering. This is particularly important in newborns and in animals like mammals that are adapted to cold environments. In humans, brown adipose tissue (brown fat) can generate heat through this process.

Step 5: Hormonal Responses
Hormones also play a role in the body's response to cold. The thyroid gland may increase the production of thyroid hormones, which can increase the metabolic rate and heat production. Additionally, the adrenal glands release adrenaline, which can also increase the metabolic rate and heat production.

Step 6: Hypothalamic Regulation
The hypothalamus, as mentioned, is the control center for body temperature regulation. It acts as a thermostat, monitoring the body's temperature and initiating the necessary responses to maintain it. If the body becomes too cold, the hypothalamus triggers the aforementioned responses to increase heat production and conserve heat.

Step 7: Long-Term Adaptations
Over time, the body can adapt to colder environments. This can involve increasing the amount of brown fat, which is better at generating heat, or increasing the efficiency of the circulatory system to better conserve heat.

Step 8: Risks of Prolonged Exposure
If the body's efforts to maintain its core temperature are unsuccessful over a prolonged period, the risk of hypothermia increases. Hypothermia is a serious condition where the body's core temperature drops below the normal range (95°F or 35°C). Symptoms can include confusion, drowsiness, slurred speech, and eventually unconsciousness. Severe hypothermia can be life-threatening and requires immediate medical attention.

Step 9: Treatment
Treatment for mild to moderate cold exposure typically involves removing the person from the cold, warming them slowly, and providing dry, warm clothing and blankets. For more severe cases of hypothermia, medical intervention is necessary, which can include warming the body core with intravenous fluids and other specialized treatments.

In summary, the human body has a complex and effective system for responding to cold temperatures. However, prolonged exposure to cold can lead to serious health risks, and it is important to take appropriate precautions to stay warm and safe.

The hypothalamus is the processing centre in the brain that controls body temperature. It does this by triggering changes to effectors, such as sweat glands and muscles controlling body hair. Heat stroke can happen when the body becomes too hot; and hypothermia when the body becomes too cold.