Homeostasis Mechanisms of Living Organism - Essay Example

Homeostasis 2007 Homeostasis (from Greek homoios – like, same, and stasis – posture, to stand) is a term meaning constant, stable condition of open or closed systems, the latter being represented by our bodies. Homeostatic mechanisms are the feedback processes taking place in our organisms in order to bring them to constant conditions. Our bodies consist of myriads of cells placed in a fluid environment, supporting the living of cells. Homeostatic mechanisms provide living-organism with an opportunity to maintain the normal condition of a number of factors necessary for circulation of fluids, such as salinity, temperature, acidity and the amount of nutrients and waste. Let us imagine that something is threatening us. The organism, preparing for action, mobilizes all its reserves of energy. Adrenals throw adrenalin in blood. The heart starts beating at great speed and we breathe quicker. The cells get more oxygen. The fluids circulate with intense. The face may turn pale or red. The body perspires. Some people, when frightened or worrying, may experience cold sweats, shortness of breath, shivering and trembling. These physiological manifestations are associated with the tendency of our body to homeostasis. Sweating is one of the displays of how our organism tries to establish the equilibrium. Why does this happen? What do we need these mechanisms for? In order to answer the questions let us see how our organisms function and how the homeostatic mechanisms work. The living processes of cells, depending on numerous chemical reactions, are provided by enzymes, a special kind of protein. Enzymes accelerate the chemical processes within cells without being used themselves. Enzymes are vital for the normal work of cells, but they also can function only in certain conditions. Temperature, salinity and acidity are the major factors influencing the ability of enzymes to work. Due to these traits of enzymes, people have learnt to conserve and preserve food products lowering temperature with the help of a fridge or increasing the level of acidity and salinity with salt and vinegar. The core of human organism is protected by skin and the internal conditions are stable and favorable for functioning of enzymes. In case, the internal conditions of the body are altered, the metabolic processes get damaged. Lasting deviations from the norm lead an organism to diseases and death. So the normal internal temperature of the body is 37° C. At the temperature of 45° C enzymes coagulate, causing death. However, people are able to survive in changing and extreme temperatures. It is possible due to maintenance of constant internal temperature. In case of stress described above the temperature should rise. Then mammals and human beings would boil quickly, while our lives are filled with strong and lasting stresses. However, it does not happen due to negative feedback control, when different receptors and effectors launch processes of stabilizing the internal conditions. The temperature of the body is detected by certain nerve cells situated in hypothalamus. This mystical part of the brain, still badly studied by scientists, is responsible for the chemical reactions and hormones in the body. So the cells of hypothalamus, called core temperature sensors, change the rate of nerve impulses. The rate of impulses generated at temperature of 37°C is taken as the set-point of the system. Each time the temperature falls below 37°C the rate of nerve impulse generation of the core temperature sensors is decreased below the normal level. When the temperature rises above 37°C, the cells generate impulses at an increased rate. When we are stressed and the core temperature is above 37°C, the signal from the core temperature sensors launches processes aimed at cooling the core. The blood vessels in the skin get the message and begin dilating, that is, enlarging in diameter. As a result they bring more blood from the core to the surface of the body, outside the insulating fat layer. Loosing heat to the external environment the blood cools. If the core continues staying too hot, hypothalamus sends a signal to sweat glands in the skin. Activated, they secrete fluid outside, moistening the skin. Evaporation additionally cools the blood. The signals from the heat sensors in the skin make us feeling hot. The organism also tends to decrease the work of muscles not to produce additional energy. The danger and necessity to act staying behind the body relaxes returning to the balanced state. Homeostatic mechanisms help us not only to cool, but also not to get frozen. Let us study the opposite case when we are exposed to cold environment and the temperature of the core falls below 37°C. The central sensor nerve cells in the hypothalamus generate nerve impulses at a lower rate. The muscles of the body get the signal to start shivering. Being a rapid alternate contraction and relaxation of muscles, shivering generates heat, going to the core. The amount of the blood that comes to the skin is also controlled by the brain. This time the blood vessels penetrating the insulating fat layer are made to constrict. While less blood comes to the surface, the heat loss is reduced. Animals have several additional ways to preserve heat. Their brain activates tiny muscles at the roots of the hairs on the skin making them stand. The air cushion, formed by the air trapped between the hairs, serves as an additional layer of insulation. Unfortunately or luckily, but in human this process causes only “goose bumps”, while our hairs are too rare to form the layer of insulation. However, this mechanism saves animals with rich fur form cold. Panting is another way animals use cooling evaporation. If we are exposed to cold for a long time, our brain launches another heating mechanism. Increasing the output of thyroid hormone secreted by the thyroid gland in the neck into the blood, which delivers the hormone to all the cells of the body, the brain makes the cells accelerate the metabolic process, thus increasing heat production (Wong, Hettiaratchi, Jayachandran, Cathers  2001). Homeostasis is one of the vital mechanisms of the body providing living for us. However, Homeostatic mechanism can be observed not only within the human body. It is the universal property of all the open and closed systems. A big corporation and mono-cellular amoebas represent the open systems of homeostatic character. The whole universe does, in fact. The tendency to equilibrium is the major law of the world’s functioning. Systems react to changes in external and internal environments launching a series of modifications directed opposite to the phenomena causing the disturbance. The goal is always the same – to maintain the internal balance. Ecological, biological, and social systems are homeostatic and they oppose change with every means at their disposal, while loosing or reestablishing the equilibrium these systems risk to get under severe constraints or perish (Rosnay 1997). Homeostasis makes complex systems ultrastable. Striving for equilibrium such systems use the tiniest opportunities, and often may behave quite unpredictable. This mechanism helps animals and human animals to survive in ever changing and dangerous environments of the world. Each time we are driven out of equilibrium, we do all possible and impossible to return the balance to our lives. This is how we evolve. As a result, homeostasis exceeds the frames of mere physiology. It turns out to be the crucial element of human existence and evolution. References: Rosnay, J. (1997), Homeostasis, Principa Cibernetica Web, Retrieved October 14, 2007 from pespmc1.vub.ac.be/HOMEOSTA.html - 9k Wong, May, Hettiaratchi, Edward, Jayachandran, Gautham, Cathers, Ian (2001), Homeostasis, Retrieved October 14, 2007 from www3.fhs.usyd.edu.au/bio/homeostasis Read More