Homeostasis from the evolutionary point of view
The origin, development and progress of a living organism depends on great measure in its ability to adapt to the environment to ensure appropriate concentrations in the internal environment. The complexity of the feedback processes that the organism uses is the result of multiple phases of evolution whose consummation is summarized in an autonomy of the human body to survive any environment or change in the outside world. The organism’s disease can be translated into a loss of the balance of internal substances caused by various alterations such as fasting, lack of sleep, protein modification and the accumulation of free radicals.
Homeostasis is a term coined by physiologist Walter Cannon, refers to the constancy or maintenance of the internal environment, even when there are variations in the external environment. For this he uses control systems that are present in all organs and tissues.
The organs of a human being are adapted to a parameter to give life. When this parameter is modified or altered either by excess or by default we can talk about physiological stress, which leads the body to an attempt to self-regulate through processes such as negative feedback.
To analyze the self-regulation situation, it is necessary to understand that it is basically made up of 3 elements: sensor, control, effector, they receive an error signal and allow its regulation in the aforementioned order.
Control mechanisms
The physical and chemical control mechanisms are formed by a set of structures connected to each other that help keep the internal environment constant. We can highlight the nervous system and the endocrine system.
The nervous system regulates the organism through nerve impulses, which are electrochemical signals that make contact with muscle effectors and glands through nerve fibers.
The endocrine system acts through hormones which travel in the blood until they reach its tissue or action organ. A clear example is evidenced in the thyroid hormone which increases the speed of the chemical reactions of all cells.
Negative and positive feedback
Negative feedback
The influence of the external environment can cause variations in the optimal range, but the organism is capable of correcting this change through negative feedback. If the organism fails to recover, we assume that it is a pathology, and if the damage persists and increases it can cause the failure of vital processes which can lead to death. In negative feedback, the regulator sends an opposite response to which the sensor informs you. The sensor gets a signal and sends an impulse, this impulse will be captured by an effector that will try to reestablish the optimal state. This type of feedback is the most common, because it allows naturally to solve a potential problem.
Positive feedback
It makes a stimulus an equal final response or the same nature as the initial stimulus, its action is contrary to negative feedback because it moves the organism away from an optimal state.
Homeostasis from the evolutionary point of view
The model for extracellular and intracellular fluid is based on the environment in which it is believed that life arose, that is, a primordial sea rich in potassium (such as intracellular fluid) that over time became abundant in sodium (similar to extracellular fluid).
Evolutionary medicine gives us concepts that can be applied to homeostasis, such as:
- Evolutionary compensation: the improvement of certain features that help the progress of the physical state can be related to the decline of other characteristics that will weaken it. Emphasizing that there will be repercussions on the state of health and disease.
- Plasticity: the change in the course of the development of a species will be influenced by the components of the environment, and the plasticity of these changes could be recognized as a result of evolved adaptive mechanisms.
- Defenses: When we present a pathology that is expressed with different signs and symptoms such as fever, we are facing an advantageous defense mechanism that, if it is disregulated, would lead to a more serious condition.
- Discordance: individuals who have evolved in an ecosystem different from that of their ancestors can present new disease risks that have not been evidenced before in the species.
Adaptive homeostasis
Adaptive homeostasis is typical of living beings, and is understood as the ability to modify the homeostatism range temporarily in response to changes that occur both in the external and internal environment. These temporary adaptations allow the survival of the individual.
However, over the years this ability to adapt is decreasing, it is believed that it is related to several factors, the one that stands out the most is the imbalance in the homeostasis of proteins (proteostasis). In addition, this will further accelerate the aging process because most cellular functions are mediated by proteins.
Proteostasis is not only based on the initial control of protein production, but also on maintaining folding, formation, function and elimination (8,10). For the correct inspection of these processes, a protestastase network is needed that includes molecular chaperones and its regulators, proteins that avoid oxidative stress and mechanisms used for proteolysis. With senescence the protestasis network decreases its function and accumulate poorly folded proteins that give way to the appearance of genetic aberrations,
Food and homeostasis
Like all body processes, food intake is regulated by homeostasis, which is why there are mechanisms that allow intermittent fasting. Indeed, the organism becomes temporarily resistant to insulin which produces changes in metabolism, which contribute to the conservation of glucose and lean fat.
Alterations of homeostasis and its consequences
Sleep:
The circadian rhythm has effects on the regulation of glycemia concentrations, stimulation of lipogenesis and in the transport of amino acids to tissue cells by controlling the level of organism to detect hormones such as insulin. Insulin desensitization can cause alteration in the homeostasis of the carbohydrates used as energy in the tissues, affecting the metabolism of carbohydrates, lipids and proteins. When there is limitation in the effect of insulin product of the maintenance of altered sleep regimes, it can result in the development of diseases such as type II diabetes and obesity .
Another point to treat is the replacement rate of cerebrospinal fluid being able to fluctuate between periods of sleep and vigil. Through studies, applying fluorescent compounds to the LCE, it was shown that in the deep sleep period the replacement rate increases. By depriving the body from sleep, the homeostasis of beta-amyloid protein can be altered;demonstrated that by its active fragment 25-35 (Aβ25-35), it has neurotoxic effects that can trigger dementia or other neurodegenerative diseases such as Alzheimer’s disease.
Lack of oxygen:
Dementia can also have a cause related to the lack of oxygen produced in disorders such as obstructive sleep apnea having serious consequences on both neuronal and glial cell viability;Also relating to the decrease in motor, cognitive and behavioral skills product of hypoxemic changes of the front and prefrontal cerebral cortex.
The lack of alveolar ventilation in these processes can also affect the pH since the accumulation of carbonic anhydride (CO2) will be combined with water whose product will be carbonic acid (H2CO3) that will reduce the body pH to a pH value < 7.36, por ende, un diagnóstico de acidosis de tipo respiratoria.
Free radicals in aging:
Free radicals are molecules that originate as a product of enzymatic reactions, aerobic processes or physical alterations of cells, this means that there is a controlled level of these radicals in the body. We have hydrogen peroxide (H2O2) product of cell oxidations that is useful as a messenger in signal transduction.
The radical redox control mechanism will be the cysteine amino acid (by its TIOL-SH group) that losing the proton forms the Tiolate ion (S-) being able to be in different oxidation states: sulfenic acid (-soh) and disulfide (-Soh) with the ability to counteract free rials forming part of the structure of new proteins. An overexidation of the taolate sulfine acid (-so2h) and sulfonic (-so3h);The consequence is damage to the proteins that are part, if not the case, aging and cell death will occur.
In short, homeostasis and diversity and complexity of mechanisms that are part of their regulation and maintenance are the key to ensuring the preservation of species and continuity of all forms of life.
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