We all know that body temperature is 36.6 degrees. But then why do we feel hot at +30 outside, since that is clearly lower? Let us figure it out. About man and his thermostat. Almost everything our body does, whether a physical load (for example, muscle contraction) or a chemical one (for example, certain stages of digestion), produces heat as a by-product. We constantly produce heat and constantly lose it, releasing it into the environment. The hypothalamus – a part of the brain the size of an almond, resting deep in the medulla – acts as a thermostat, trying to keep the amount of heat created and the heat lost at the same level, thereby maintaining a normal body temperature. This is not such a difficult task, since heat strives toward equilibrium – a state in which everything around has the same temperature. That is why a bowl of hot soup and a glass of ice water will reach room temperature if you leave them on the table. Cool down and not boil over. Usually the environment is colder than our body, so our little thermostat can simply dump the excess heat into it using thermoregulatory processes such as sweating (when heat is lost through evaporation) and increasing blood flow through the capillaries near the skin's surface (where heat is lost through radiation, convection and conduction). When there is a large temperature difference between our body and the environment, heat very easily leaves us into the air, and we quickly «cool down». When the environment is warmer and closer to our body temperature, heat is not transferred as easily and quickly through radiation, convection and conduction. The excess heat has to be retained longer, and so we feel hot and uncomfortable. And if the ambient temperature is higher than body temperature, the tendency of heat toward equilibrium begins to work the other way, and we start to absorb excess heat from the environment. Breaking into a sweat. If the weather is hot and dry (as in a desert), the body can cope with it by increasing sweating in order to get rid of more heat through evaporation. When it is hot and humid outside, tolerating the heat becomes harder, because the high moisture content in the air simply does not allow the sweat to evaporate. If we spend a lot of time in a situation where the heat we produce or absorb from the environment exceeds the heat we get rid of, body temperature will rise, and the body begins to suffer from heat-related illnesses.