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Another way in which the human body works to keep things in balance is by maintaining a steady temperature. Mammals and birds are known to be warm blooded, which is also known as homeothermic, which means that their body temperatures are kept constant even if the temperature in the surroundings changes. Humans have a body temperature of around 37C which means that your body will try to maintain this temperature if you are in freezing or tropical temperatures by making specific changes. Other animals, such as lizards, are cold blooded. This is because a lizard has a body temperature of around 20C.
A homeothermic animal can keep its temperature constant by physiological changes that cause it to generate or lose heat. They are also known as endotherms which means ‘heat from the inside’. The way that this is done is through chemical reactions within the cells of the endothermic animal which can create heat. As well as this, these animals can regulate the amount they sweat and blood flow through the skin in order to release heat from the body when needed.
The reason that an animal needs to keep a steady temperature is so that it can have consistency. Since many chemical reactions happen in living creatures, keeping a steady temperature allows these to happen without an external factor (outdoor temperature) affecting the process. This means that the metabolism, among other processes, can be steady year-round.
Monitoring body temperature
In mammals, the area that monitors temperature is known as the thermoregulatory centre. This is located within the brain and is a bit like the body’s thermostat – it tracks the temperature and adjusts things accordingly.
When in a cold or hot environment, the skin will react to this stimulus by sending electrical impulses to the brain. These nerves then send messages to organs within the body to regulate temperature in the same way we have already explored.
The skin within temperature control
The skin plays a massive role in controlling temperature for humans. It is made of three different layers: the epidermis, the dermis and the hypodermis. The outer epidermis is made of dead cells that prevent water loss and act as a form of protection from bacteria. The hypodermis is made of fatty tissue that acts to insulate the body and stop the loss of heat energy. The middle layer, the dermis, contains sensory receptors and is the location of sweat glands and hair follicles.
When the temperature gets too high and the body needs to lose heat, sweat is secreted onto the skin’s surface. This process allows the body to lose heat as, when a liquid evaporates to a gas, heat is required which is supplied by the body. The body therefore loses heat by turning the liquid sweat into a gas.
Another way that the skin works to maintain temperature is by using hairs on its surface. There are tiny muscles that can control the hairs on the skin and cause them to become erect. In cold conditions, the hair erector muscles contract so that the hairs stand on end. This traps a layer of air next to the skin. As air is a poor conductor of heat, this layer of air next to the skin works as extra insulation. In warmer conditions, the hairs lay flat so that no air is kept, as this insulator is not required. This process is not particularly useful for humans but in animals with longer hair it is used very often. Another way in which the skin can control temperature is through the blood vessels in the dermis. These capillary loops (small blood vessels) become dilated when the body is too hot. This works to send more blood past the surface of the skin which releases heat. This process is called vasodilation. In cold conditions, the opposite to this happens. The blood flow is restricted to the skin so that the heat that is in the blood supply is not lost through the surface of the skin. This process is known as vasoconstriction.
