Thermostats are devices that keep temperature at the desired level. They are used in refrigerators, dishwashers, electric ovens, water heaters, washing machines, and central heating. Without a properly functioning thermostat, the devices or machines are likely to break down.

Did you know that there is also a thermostat in our body that comes with a lifelong guarantee? How about the fact that each is customized for each body? The thermostat in our body is so durable and dependable that it continues to regulate our body temperature for a life time, through illness and health, and good and bad weather.

Hypothermia and hyperthermia

When you are alive and kicking, your thermostat works within a temperature range of one degree (36.5 °C–37.5 °C). If your body temperature taken in your mouth is above or below this range, it means that your body is signaling certain problems. Temperatures below 35°C lead to hypothermia, while those above 39°C cause an opposite problem called hyperthermia.

Hypothermia is a drop in body temperature, generally due to such factors as rain, wind, snow, or cold water. Prolonged hypothermia first causes shivering and blackout, then death. People who fall into water in shipwrecks die more of hypothermia than of drowning.

Hyperthermia, on the other hand, is a condition in which the body temperature rises to high levels because of factors such as inflammatory diseases and prolonged exposure to sunlight. If it continues for long, hyperthermia causes fatigue, dizziness, nausea and problems in blood pressure. It may lead to seizures or death, especially in children, unless immediate aid is provided.

Where is our thermostat?

Whether you inhabit Siberian taigas or African deserts, your body temperature is kept within the normal range. Our thermostat, called the thermoregulation center, takes up a small place in the hypothalamus of our brain. Assigned the task of balancing our body temperature, the center activates the system to decrease the temperature when it rises and to increase it when it drops. The center is composed of two parts, one in the front of the hypothalamus and the other in the middle. The former is in charge of decreasing our temperature, while the latter of increasing it.

It is the receptors beneath our skin that activate the center. The receptors have two types of heat sensors, one for warmth and the other for cold. A change in temperature, even in an extremity like the toes, is immediately reported to the center, which switches the system on. If the body temperature needs to fall, then the perspiration mechanism is switched on. To do this, the temperature inside the body is first transferred to the skin. The most important process at this point is the expansion of blood vessels, which induces a heat transfer. If the body temperature needs to be raised, the vessels are contracted and shivering is induced.

Adjusted for all conditions

Our thermostat is programmed to make maximum use of our body temperature and make adjustments depending on our age, whether we are asleep, hungry, ill, and according to weather. The required amount of energy is different for babies, children, teenagers, and the elderly. The human body needs energy less during sleep and more during an illness.

No one’s body temperature remains at the same level at all times. Our body temperature is unique to us, just like our fingerprints, and it can be measured through precise measurements. The factors that affect our body temperature may be as diverse as what we eat, what we do, what we wear, our mood, our hormones, and the environment. The increase in an adult’s body temperature due to activity is less than that of babies and children.

Our body has a temperature cycle which changes throughout the day. When we wake up in the morning, for example, our body temperature is 0.5 degrees lower than it is during the day. It is at its lowest in the second half of the night. It is highest between 16:00-18:00. We have greater heat exchange in cold weather than in hot weather. The heat regulation center adjusts temperature in response to all these changes, and thus saves energy.

Our temperature changes according to our gender, too. Body temperatures obtained from mouth measurements have shown that they may change by ±1.4 degrees in women and by ±1.2 in men. Hormones also play a role in this difference. For example, women have unique body temperatures during their period and pregnancy.

The temperature of the organs

Some parts of our body and some of our organs require different temperatures. The warmest organs are at the inside: the liver is 41.3 degrees on average, for example. Our skin is 33 degrees, and the parts near the skin have relatively lower temperatures. The temperature of the inside of our mouth, for example, is lower than that of our skin. The temperatures in the armpit and in the ears are likewise different. The thermoregulation center also has an impact on the rates of the chemical reactions taking place at the cellular level, as it keeps every one of the organs working at optimum temperatures.

There is incredible wisdom in how our body is heated (or not). Body parts that interact with the outside world have lower temperatures. One of the advantages of this is that it maintains optimum energy consumption. The higher the temperature difference between two objects, the easier the heat exchange. If our skin were as warm as our average temperature, i.e. 37°C, we would lose more heat at higher rates.

Furthermore, our eyes are granted a very special mechanism. The eyes, almost 90% of which are water and whose surface must be kept moist, are in constant contact with the outside world. However, the eyes of people who live in cold climates, where the temperature can reach -50°C, do not freeze because the eyes are placed in a protective shelter and wrapped in muscles, lipid layers, and eyelids. What’s more, capillaries, which are extensions of the ophthalmic arteries that encircle the eyes like a web, carry warm blood to the eyes regularly. Additionally, the fact that tears are salty lowers their freezing point.

Temperature balance in other living things

Animals also have body temperatures ideally programmed for their functions. The hedgehog, for example, has a body temperature of 36°C, but it is dropped to 6°C during hibernation. The body temperatures of most mammals are kept at about 37°C.

Animals are similarly endowed with systems of temperature cycles as required by the climatic and environmental conditions in which they live. For example, the body temperature of the oryx, an African antelope, can rise to 45°C when it is on the run. It can withstand such a deadly temperature thanks to the perfect system that protects its brain. The oryx has a peculiar network of vessels at the lower side of the brain which decreases the body temperature due to heat loss caused by evaporation. The carotid artery separates into smaller veins in the sinus cavity before it carries the blood to the brain, which causes the blood to lose heat. When the blood reaches the brain, it is already cool enough for the brain to function properly.

The creation of such systems certainly are miraculous, and yet we never think about them. All of our needs are met without our knowing about it.