Regulatory mechanisms: what they are and how they make the body work

Living beings, both animals and plants, are open systems that obtain nutrients and gases from the environment and excrete waste substances in our environment continuously. What for us are feces, for other microorganisms and invertebrates are succulent substances that become part of their tissues (organic matter), thus allowing the continuation of the carbon cycle within the trophic chains of the ecosystems.

Being an open system is necessary for survival: energy is neither created nor destroyed, it is only transforms (according to the energy conservation law) and, therefore, we must obtain it from the environment continually. However, this also has several negative points, as we constantly dissipate heat in the middle, we depend on our environment for all our biological tasks and we can get sick and die as a direct consequence of what happens in our environment.

To put some order in the changing chaos that is the environment, our bodies present a series of biological and / or physiological regulatory mechanisms

to maintain a stable internal condition, compensating for changes that may occur in the environment. Let's see how they are.

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What is a regulatory mechanism?

In biology, a mechanism is is a system with parts that interact causally, giving rise to processes that have one or more effects on the environment, be it internal, external or both. One mechanism can be the process that leads to the sweat of the human being in a hot moment (physiology), but natural selection or genetic drift are also considered mechanisms, although in this case of a nature evolutionary.

In the world of regulatory mechanisms, nothing is black or white, since Biological entities are extremely complex beings (multicomponential), whose systems are in continuous interaction and feedback. Beyond its diversity, three great levels can be distinguished in the underlying mechanisms of a living being:

• Genetic mechanisms: lowest in the hierarchy. The functioning of genes and their expression is essential, but they correspond to the basal substrate of any system.
• Mechanisms of cellular functioning: the next mechanism is that which concerns the cell, and therefore the organs and tissues of the body.
• Nervous and endocrine mechanisms: they are the most advanced regulatory mechanisms on the evolutionary scale.

All living beings have genetic mechanisms, because by definition, a cell must have a genome to self-replicate on future occasions (even if it is only one chromosome, as in bacteria). On the other hand, every living entity must present at least one cellular regulation mechanism, since the basic unit of life is the cell, although it makes up the entire organism (as is the case with bacteria and archaea).

As you can imagine the pinnacle of physiological regulatory mechanisms (glands and neurons, which are part of the endocrine and nervous systems, respectively) is restricted to the most evolutionarily animals complex, as we are vertebrates, although other living beings also have their own nervous and endocrine scales.

At this point, it should be noted that regulatory circuits can present two feedback systems (feedbacks): positive and negative. We explain what they consist of in a brief way in the following lines.

1. Negative feedback

This time, the regulation mechanism seeks to keep a parameter X under control in a very specific spectrum, always close to the value X0, which is the maximum optimum in a specific environment. The values ​​of the parameter X are collected from the environment or internal environment through information channels (such as thermoreceptors and other nerve groups) and the information is brought to the center of the mechanism, which will generate responses based on the environment in the best way possible.

2. Positive feedback

In this case, things change. The objective of positive feedback regulation mechanisms is reach the maximum point of effectiveness of parameter X, deviated from the value X0, once certain conditions have been reached.

Although we move in quite complex concepts, the difference between a negative and a positive feedback is very easy to understand: in the first case, the The system responds to a direction opposite to the signal, that is, it tends to “stabilize” the system output so that it remains in good condition constant. On the other hand, in positive feedback the effects or outputs of a system cause cumulative effects at the input. In the latter case, it is a system that, by definition, presents an unstable equilibrium point.

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Examples of regulatory mechanisms

We have moved between quite ethereal concepts, so it will be useful to exemplify a little what a regulatory mechanism is from a physiological point of view. Let's say, for example, that we want to understand how sweating occurs in humans. Go for it.

First of all, it should be noted that sweating is a regulatory mechanism modulated by the sympathetic nervous system, which is responsible for many involuntary functions in humans. Our hypothalamus it contains neurons in the anterior and preoptic area specialized in recording changes in internal temperature and in the activity of the cerebral cortex. Therefore, when the information arrives that there is excess heat (be it internal or external), the hypothalamus sends the signal through cholinergic fibers to the eccrine glands throughout the skin so that excrete sweat.

Sweat comes out through the pores that connect the eccrine glands with the skin. Since fluids need heat to evaporate (after all, heat is energy), they "catch" this excess body surface temperature, which causes our general system to become cool down. Through the evaporation of sweat, 27% of body heat is dissipated, so it is not surprising that this mechanism is activated in the event of any physical and / or environmental variation..

In this case, we are at a theoretical level before a negative feedback regulation mechanism. The organism's interest is to maintain body temperature (parameter X) in a suitable range as close as possible to the ideal, which is between 36 and 37 degrees. In this system, the functional complex responds inversely to external stimuli.

If we get philosophical we can also conceive of natural selection or genetic drift as regulatory mechanisms from an evolutionary point of view. Natural selection exerts pressure on the open system that is a population, selecting the genes that are most beneficial in the long term and disregarding the least adaptive ones.

For example, an animal of a bird species that is born (by a de novo mutation) with a longer beak larger than the rest, it might be easier to hunt insects among the barks trees. As this living being has an advantage over the rest, it will be able to feed more, it will grow more and, therefore, it will be stronger when it comes to competing with the rest of the males to reproduce. If the “big beak” trait is heritable, it is to be expected that the offspring of that animal will be more viable than the rest.

Thus, over the generations, the “big peak” trait would increase in the population, since simply those that present it live longer and have more opportunities to reproduce. Natural selection acts as a clear evolutionary regulation mechanism in this case, since the proportion of genes in a population varies according to the impositions of the environment.

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Resume

As you may have seen, regulatory mechanisms in the world of biology go far beyond thermoregulation or energy consumption. From the expression of genes to the evolution of the species, everything can be summarized in a positive or negative feedback that seeks to reach a maximum point of effectiveness, at one point or another. In the end, the goal is to achieve the maximum internal balance in every possible way, always taking into account environmental constraints.

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