What does our body do to keep cool in summer?

Humans keep body temperature constant at about 37 ⁰C. In other words, we are homeotherms. Since we are in summer, we will examine how the body responds to heat.

To maintain body temperature our body uses thermosensors, which report our thermal state to the hypothalamus, a small neuronal device in the brain. If it detects any change with respect to the ideal temperature, it starts up the necessary mechanisms to correct it and return to the normal temperature.

Summarizing things a lot, in summer the goal of our body is not to gain heat but to lose it. Since our main source of heat is metabolism itself (we are endothermic animals), the less activity we display, the less heat we will produce and, therefore, the less we will heat up. That is why it is advisable not to do physical work. Eye: think, read and study are not physical activities.

Although the environment is not our main source of heat, we should not stay in warm environments, bathe in hot water and sunbathe. It is easily understood that running in full sun is not recommended.

How do we lose heat?

The body loses heat through three ways.

One is the direct transfer to a material with which it is in contact. We call it conduction when it is transferred to an object and convection if it is received by a fluid. The intensity of the heat transfer in this way depends on the temperature difference between the body and the material with which it is in contact. The greater the difference, the more it is transferred.

This transfer is greater when it occurs at a mass of water than one of air, because the thermal conductivity of this is 23 times lower than that of that. A 17 ⁰C bath cools much more than staying naked and dry out of the water at that temperature.

Another transfer path is the emission of infrared radiation, electromagnetic waves of greater length than visible light. It occurs between objects that are at different temperatures, from the hottest to the coldest, and their intensity depends on the thermal difference.

In summer it is a form of insidious transfer. In hot weather it is normal for objects and materials found in our immediate environment to be as hot as our body. For that reason it is not easy to lose heat like this at this time, and we are even likely to win it.

Finally there is evaporation, the most effective mechanism to lose heat. The liquid that evaporates our body is the humidity of the respiratory tract (perspiration) and sweat (perspiration). Perspiration is not physiologically controlled in humans (yes in dogs, for example, through panting), but perspiration is.

Evaporation is very useful because it cools us even if the environment is warmer than our body. That is because evaporation needs a contribution of heat, so that the skin loses it, even if it is colder than the air around us. It is a very effective way of cooling because to evaporate a milliliter of water you need 560 calories. This is 5.6 times more than the heat needed to heat that same volume from 0 hastaC to 100 ⁰C.

This route has two limitations. One is that the intensity of evaporation decreases when the humidity in the environment increases: that is why humid environments are suffocating. The other is that you have to drink water to replace what we lose by sweating and, depending on the circumstances, you also go out. That's why it's important to drink when it's hot. By the way, with age you lose the ability to experience thirst. Therefore, when it is hot, older people should drink water even if they are not thirsty.