Homeostasis PDF

**HOMEOSTASIS** Every organism, be it plant, animal or microorganism, is composed of a complex system of chemical processes. These processes are self-regulating and do maintain a steady state within an external environment which is liable to change due to continuous state of flux. The ability to ma...

**HOMEOSTASIS** Every organism, be it plant, animal or microorganism, is composed of a complex system of chemical processes. These processes are self-regulating and do maintain a steady state within an external environment which is liable to change due to continuous state of flux. The ability to maintain this steady state within a constantly changing environment is essential for the survival of living systems of organisms. In order to maintain this condition, organisms develop a variety of structural, physiological and behavioural mechanisms to achieve and attain the steady state. This engenders the preservation and constant maintenance of a steady state of the internal environment. This refers to the concept of homeostatsis. Homeostasis is a property of biological systems where the self-regulating process tends to maintain a balance for survival. The regulation takes place in a defined internal environment that is unique for every individual organism of a population. It is a concept in physiology, the branch of biological science that seeks to explain the physical and chemical mechanisms that are responsible for the origin, development and progression of life. Each form of life, from the acellular and simplest virus (a living entity) to the largest mammal (whales) or tree or even the complicated human body, has its unique functional characteristics. As a concept, homeostasis was first noted by Claude Bernard through his research into how organisms regulate their physiological conditions such as body temperature, water content, electrolyte content, etc. and maintain them in a steady state although within fairly narrow limits. As such, Bernard declared that "the constancy of the internal environment is the condition for free life". This was interpreted to imply that the constancy of the internal environment of cells is basically the condition for free life. The internal environment here refers to the immediate surrounding of cells in the body of organisms. For instance, 50% to 70% of the adult human body is fluid. This is mainly a water solution of ions, electrolytes and other substances. The fluid is of two types -- intracellular and extracellular. Most of the fluid is inside the cells, called intracellular fluid. However, about one-third of the fluid is present in the intercellular spaces outside the cells and is called extracellular fluid. It is also referred to as intercellular, interstitial or tissue fluid. This represents the internal environment of the cells as noted by Bernard. The internal environment is in constant motion throughout the body of a given organism, which must be made so (constant) to attain a stable homeostatic condition and invariably good state of health and well-being. When disrupted from being constant, disease set in. The regulation of homeostasis depends on three mechanisms -- (i) the effector, (ii) the control centre and (iii) the effector. On a general note, cells are surrounded by tiny channels and spaces which are filled with the tissue fluid. This fluid provides the cells with the medium in which they live. Overall, this represents the internal environment of the organism. It is this internal environment that must be kept constant largely because as the basic constituent of the organism, they need to continue to carry out various vital functions. In actual facts, cells are capable of living and performing their special functions as long as the proper concentrations of oxygen, glucose, different ions (electrolytes), amino acids, fatty substances and other constituents are available in this internal environment for transport into the cells when needed. The intracellular fluid contains large amounts of potassium, magnesium and phosphate ions instead of the sodium and chloride ions found in the internal environment. The extracellular fluid of the internal environment of cells contains large amounts of sodium, chloride and bicarbonate ions as well as nutrients for the cells such as oxygen, glucose, fatty acids and amino acids. It also contains carbon dioxide transported from the cells along with other cellular waste products. Special mechanisms for transporting ions through the cell membranes maintain the ion concentration differences between the intracellular and extracellular fluids. Much later, Walter Canon, an American physiologist introduced the term "homeostasis" stemming from "homeois" -- same and "stasis" -- standing. This describes how the constancy of the internal environment, expounded by Bernard, is maintained. Homeostatic mechanisms physiologically maintain the stability of the cell environment as mentioned earlier. In doing so, the mechanisms provide the organism with a degree of independence of the environment. When effective, the organism will be independent of the external environment and would survive in it. This represents a measure of the success of the organism to exist in a given environment. As such, complex organisms such as mammals or flowering plants are able to maintain relatively constant levels of activity despite fluctuations in environmental conditions. This implies they are capable of regulating their internal environment to suit the prevailing external environment. In order to attain the stability under reference, the activities of organisms need to be regulated at all levels of biological organization, commencing from the molecular level, DNA level, gene level, chromosomal level, cell level, tissue, organ, system, organism up to population level. **Formation of the Human Tissue** **Fluid** The tissue fluid is formed from the blood. This is done by the process of ultra-filtration in which small molecules and ions are separated from the relatively larger molecules. When blood reaches the arterial end of a capillary, it is then under intense pressure due to i. pumping action of the heart and ii. the fine bore of the capillaries transporting the blood. i. respiratory gases (O~2~ and CO~2~)diffuse, ii. cells extract their metabolites and iii. unwanted excretory waste products are removed. i. chemical constituents e.g. glucose, ions, electrolytes etc., ii. osmotic pressure, which is determined by the relative amounts of water and solutes iii. the level of carbon dioxide and iv. cellular and intercellular space temperature. - Homeostasis is the ability to maintain internal stability of a defined biological system (organism), in response to environmental changes. - Body systems that are involved in maintaining the homeostatic conditions in humans as well as other animals are the endocrine and nervous systems. For other groups of organisms, other organs play this key role. - Homeostasis is essential to organisms as it is a self-regulating process that controls internal variables necessary to sustain life. - The main components of homeostasis are (i) the receptor, (ii) the control centre and (iii)the effector. - The receptor receives information on the changing internal environment. - The control centre processes the information as received, detailing what has to be done. - The effector responds to the commands of the control centre by enhancing or opposing (as the case may be) a given stimulus. - The primary function of homeostasis is to maintain a balance within the body of an organism regarding a changing stimulus -- temperature, salt concentration, electrolytes, nutrient levels, pH levels, among a host of others. - In order to maintain the homeostatic condition of an organism, cells perform the following functios: (i) obtain and use nutrients in form of energy, (ii) exchange materials (ridding of waste products and receive new imputs), (iii) make/produce new cells through growth and (iv) eliminate wastes through body waste removal mechanism peculiar to the organism.