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“Homeostasis maintains a dynamic equilibrium of internal and external variables within set limits that allow cells of the body to continue their function.”

Homeostasis means, the same – standing still, homeostasis is attempting to maintain a dynamic equilibrium, however there are multiple internal and external factors that may affect homeostasis of the human body (Cannon, 1932). Physiology allows an understanding of how the body reacts to such a change in variables. Exercise may increase body temperature and the body will react in a multitude of ways to cool itself and return the body to homeostasis. (Gray & Cooke, 2008). Enzymes are proteins that help speed up chemical reactions in cells. Enzymes require optimum temperatures of 37oC and pH level (dependent on location) in order to function, an increased temperature will initially increase the rate of chemical reactions until such time when the enzymes become denatured, loss of solubility and communal aggregation takes place, similarly with temperatures that drop below the optimum. The active site becomes unrecognisable by its substrate in conditions beyond optimum pH and temperature thus reducing chemical reactions and life processes (Sanchez-Ruiz, 2010).

Homeostasis aims to allow the body to continue its activities of daily living regardless of the external environment or ingested products via maintenance of the internal environment. The internal environment is made up of twelve litres interstitial fluid and three litres plasma, the interstitial fluid provides cells with energy in the form of oxygen, glucose and other nutrients, cycling the waste into the blood to be filtered out of the body. This highlights the need for homeostasis to maintain blood pressure at an optimum level to facilitate the profusion of blood through the tissues ensuring processes continue within the intracellular fluid (Ankney et al, 2012). Equilibrium may be found via diffusion, being the movement of particles from an area of high concentration to that of an area with low concentration gradient, homeostasis allows diffusion to continue until such a time the factors have returned to their set limits. Osmosis is a special type of diffusion that allows water molecules to pass through a partially permeable membrane, once equilibrium is achieved in this instance, volume may be different but concentrations would be the same, the movement of molecules across the membrane at this point would be the same (Alharbi et al, 2014).

Negative feedback instigates such processes into action, either inhibiting processes or initiating others in order to return to homeostasis. Stimuli produce a change in a factor, such as an increased temperature due to exercise, the change is detected by receptors and the information is sent along afferent pathway to the control centre. Information is then sent to the effector via the efferent pathway in order to return the variable to homeostasis. Without this negative feedback loop, the temperature in this instance would rise like that in a positive feedback mechanism. Homeostasis reverses changes, hence the term negative feedback (Keesey & Powley, 2008).

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The endocrine system assists with functions of the body, through growth, reproduction, metabolism, emotions and balancing of water and electrolytes, also dealing with adaptations to environmental changes as well as stressors. The endocrine glands of which there are many, secrete a number of hormones in order to achieve their goal and maintain homeostasis (Ankney et al, 2012). The endocrine system responds slower however the effect is longer lasting excluding the instance of a ‘fight or flight’ situation. The stimuli is noted by the receptors, prompting hormone release, which may bring about a necessary change of the parameters of homeostasis to overcome the obstacle, in order to return to a natural homeostasis. These hormones are sent via the circulatory system and connects to the target cell via a receptor and