Homeostasis is the capacity of living organisms to maintain their internal stability of bodies, as appropriate to the temperature and pH (acidity and alkalinity balance), through the exchange of matter and energy with the environment.
This occurs thanks to various systems of metabolic self-regulation that sustain the dynamic balance necessary for the preservation of life.
Thus, faced with the appearance of changes in the conditions of their environment, living beings can respond through one of the following strategies:
- Evade . It consists in attenuating or diminishing the internal impact of these environmental variations by means of some escape mechanism, such as varying habitat to a more convenient one or assuming resistant forms to the environment.
- Conformity . The interior of the living being varies with the environment, given that its regulation is not efficient, so it must adapt gradually or “acclimate” to the new conditions.
- Regulation . In the face of environmental change, the living being performs compensatory actions that keep the inside of his body in a relatively constant condition.
The homeostatic processes , however, do not operate entirely in the four categories, as no organism can be a regulator or absolute conformista. The most usual is that a mixture of the three strategies is produced, depending on the variant environmental factor and the nature of the creature.
It can also be understood as a form of homeostasis the regulation of internal chemical balance by mechanisms of excretion, or the maintenance of glucose levels through hormonal secretionand glycogenesis or glycogenolysis (in cases of abundance or shortage respectively).
Examples of homeostasis
- Sun exposure . It is common to see reptiles, animals unable to regulate autonomously their interior temperature (cold-blooded animals), expose themselves to the sun to increase their body temperature and energize their metabolisms.
- Hibernation . Bears and other mammals usually shy away from the crudities of winter (snowfall, rain, low temperatures, little food) entering caves or burrows away from the impact of the elements. There they slow down their metabolisms and subsist with a minimum of energy consumption, sustained by lipid reserves previously built.
- Shiver . In the face of a sudden decrease in the ambient temperature , the body of the other homeothermic animals gives a nervous signal to their muscles to generate a tremor that generates muscle heat and counteracts a bit the cold.
- Regulation of glucose . As we said before, in the face of the decrease or the superabundance of sugars in blood, the human organism activates a hormonal apparatus destined to accelerate the synthesis of glucose (and formation of reserve lipids) or to extract it from said lipids or, if it were necessary, of muscle fibers and other tissues, in order to maintain levels within the appropriate. The organ in charge of these tasks is the pancreas.
- Shun the sun . In conditions of extreme solar exposure, such as deserts or extreme weather seasons, reptiles and cold-blooded animals seek shelter under leaf litter, rocks or even underground, chasing the freshness of such environments to calm excess heat in their bodies .
- Vasodilation . When we enter very hot environments, our body orders the widening of the blood capillaries, increasing the surface of them exposed to the environment, and thus allowing the loss of excess heat and cooling the blood.
- Vasoconstriction . The opposite of vasodilation takes place in low temperature environments, in which the capillaries are closed to minimize the amount of blood exposed to the cold and thus preserve the blood heat as much as possible.
- Goose bumps . The so-called “goose bumps” is another homeostatic mechanism, because it allows the cutaneous hairs to erize and attenuate the amount of heat radiated by the skin. It is an evolutionary reflex that has remained despite the loss of some kind of coat covering our biological ancestors.
- Sweating . It consists of the secretion of liquid substances on the skin, whose evaporation cools it and makes it possible to alleviate the increase in interior temperature.
- Ammonia control . While ammonia is a substance linked to our digestive processes, which provides the necessary nitrogen for various amino acids and proteins , its levels in the human body must be monitored by the liver. This organ is able to convert the surplus of ammonia into urea and expel it through the urine formed in the kidneys. Otherwise, the increase of ammonia would lead to a deterioration of the functioning of the organism.
- Lingual perspiration of dogs . The usual image of the dog with the tongue out is due to the fact that it is the species’ way of exchanging heat with the environment, since the dog’s tongue contains a lot of blood supply and allows a refreshing when extracted from the body.
- The acceleration of breathing . When mammals are in environments of low oxygen concentration, or when oxygen levels in the blood are too low for cellular demand (when we exercise, for example), an immediate response emerges that accelerates respiration to increase the proportion of breathed air. At the same time, the heart beats faster and blood pressure increases, promoting a better oxygenated blood supply to the body.
- The cellular homeostasis . In the process of regulation of the internal pressure of the cells (osmotic pressure), they release or absorb surrounding content through the selectivity of their plasma membranes, until they have the concentration levels suitable for their stability.
- Regulation of blood pH . The ordinary metabolism of our bodies generates quantities of acid waste that attack the appropriate level of blood acidity , whose compatible borders with life are between 7.0 and 7.7, so they must be discarded as soon as possible by means of various monitoring and biochemical control systems.
- The immune system . While it keeps at bay the intrusive elements that could cause inconveniences to the organism, our immune system acts as a mechanism to preserve the homeostasis of the system, perpetuating its stability in the face of possible infections or pathologies, even when these have already managed to penetrate the body