It is well documented that human beings are capable of thriving and surviving in the harshest of conditions ranging from the arctic to the equator and with different forms of lifestyles and diets. One of the reasons’ for this is not farfetched, it is the ability of the human body to adapt to various conditions and in turn maintain homeostasis. Homeostasis refers to the human body's ability to regulate her internal environment physiologically in a bid to ensure and maintain stability in response to the instability and fluctuations of the weather and the external environment. Also, homeostasis refers to the special mechanisms that are in place in the human body that detect physiological changes and also respond to the physiological changes from their various set point values through initiating responses which restores them to their optimal physiologic range. To maintain homeostasis, there is collaboration between all the systems in the body, though the various systems have well defined specific roles they perform. Of all the systems in the body, the endocrine and nervous systems are very important in maintaining homeostasis. Important basic functions in the body such as breathing and heart rate may be stimulated or slowed by the nervous system. Also, hormones help with maintaining balance of fluids and electrolytes in the body. The kidneys, liver and brain are all involved in maintaining homeostasis. The liver which is an abdominal organ and the second largest organ in the body after the skin is saddled with the task of removing toxic substances from the body and also involved with carbohydrate metabolism. The kidneys which are paired retroperitoneal organs are responsible for the regulation of blood water levels, maintenance of ion and salt levels in the body, reabsorption of non toxic substances into the blood, regulation of blood pH and excretion of urea and other wastes in the body. The brain through the endocrine system, the autonomic nervous system and the hypothalamus maintains homeostasis in the human body. Homeostasis is very germane to the body as the body needs it to stay alive. Failure of the human body to maintain homeostasis may lead to a disease state or death. For example, a serious disease state such as heart failure occurs when the negative feedback mechanisms in the body become overworked and deleterious positive feedback mechanisms supervene. Other disease states which could occur due to the imbalance of the homeostatic mechanisms in the human body include heat stroke, dehydration, gout, hyperglycaemia, hypoglycaemia and diabetes to mention a few.
Physical health solely depends on an optimally functioning homeostatic mechanism. Undue and persistent stress such as poor or inadequate sleep, unaccustomed exercises, and inadvertent build up of free radicals in the body, drug abuse and alcoholism are capable of disrupting the body's homeostatic mechanisms which ultimately leads to a disease state. When this happens, medical intervention can help restore the body to the pre-illness state through the actions of the homeostatic mechanisms.
There are several examples of homeostasis in the body; some of the very important ones include acid-base balance in the body, temperature regulation, glucose metabolism, calcium metabolism and body fluid volume. Negative feedback mechanism is an integral part of the proper functioning of the homeostatic mechanisms. It literarily means that whenever there is a change in any of the systems, there is an automatic corrective mechanism which initiates the reversal of the noxious change and brings back the body to the set point also known as the normal.
In the simplest of languages, negative feedback could be likened to an oven in use. When it gets too hot, the mechanism that causes the increase in temperature resulting in the heating turns off automatically which allows the oven to cool down. It eventually gets cold since the heating system has been turned off automatically, the heating system then turns on again increasing the temperature of the oven. In essence, a system exclusively controlled by the negative feedback mechanism is never maintained perfectly as it swings about the set point. However, an efficient homeostatic system reduces the size and frequency of the oscillations. Regulation of the body temperature is an integral part of homeostasis in the body. Animals which maintain a near normal body temperature are called endotherms and sometimes referred to as warm blooded animals. Normally, they maintain their body temperatures between thirty five degrees Celsius and forty degrees Celsius. Mammals and birds are ectotherms. On the other hand, ectotherms have variying body temperatures, though some of them could have warm blood during the day either by basking in the sun or through extended muscle activity such as tuna and bumble bees. The main difference between ectotherms and endotherms is that endotherms utilize internal corrective mechanisms to maintain homeostasis while ectotherms utilize behavioural mechanisms such as moving into the shade or a cool place when hot or lying in the sun and basking when they feel cold. Body temperature in human beings is controlled by the thermoregulatory centre in the hypothalamus; impulse is received from receptors in the hypothalamus and receptors in the skin. Both are thermoreceptors. The hypothalamic receptors monitor the core temperature which is the temperature of the blood is it navigates through the brain. Receptors in the skin especially those on the trunk monitor the external temperature. The two sets of information are required for the body to make appropriate adjustments, impulses are then sent from the thermoregulatory centre to the different effectors to adjust the body temperature. Whenever we are faced with unbearable heat or a very cold weather, we may take off our clothing’s when too hot or put on extra clothing’s when too cold. However, when these responses are inadequate, the thermoregulatory centre is then stimulated. The heat loss centre of the hypothalamus is stimulated when we feel too hot and the heat conservation centre is stimulated when we are too cold. During excessive heat, vasodilatation, sweating, pilorelaxation and stretching out all help the body loose heat. The arterioles increase in size so as to allow more blood into the capillaries in the skin leading to heat loss. Also, sweat glands secrete sweat in response to heat. The sweat produced removes heat from the body and gives a cooling effect on the body. Also, hairs on the skin are laid flat. This prevents whatever trapped air from heating the body by insulating it. Likewise, when the body feels too cold vasoconstriction, shivering, piloerection all occur. The arterioles reduce in calibre and get smaller reducing blood supply to the skin to keep the inner body warm. Also, rapid contraction and relaxation of the skeletal muscles leads to shivering which produces heat to keep the body warm. Curling up and making the surface area of the body smaller reduces the effect of the cold on the body. In addition, the hairs on the skin rise, giving rise to goose pimples thereby trapping hair between the skin and the atmosphere creating an insulation against the cooler air.
In conclusion, Homeostasis is highly important for the survival of living beings so as to regulate the milieu of the body which is subject to fluctuations periodically as various disease states and even death may occur due to a faulty homeostatic mechanism.
References
http://www.biologymad.com/resources/A2%20Homeostasis.pdf
http://course.zju.edu.cn/532/study/theory/1/int/pdf/01-homeostasis.pdf
L.A Zaykoski., Examples of Homeostasis in the body.,http://www.brighthub.com/science/medical/articles/112024.aspx., Retrieved on 25th December, 2012.
http://www.biologymad.com/resources/A2%20Homeostasis.pdf
http://scienceray.com/biology/human-biology/a-guide-to-human-homeostasis/
