Why homeostasis is a central theme in animal physiology

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Why homeostasis is a central

Theme in Animal Physiology?

Homeostasis is the name given to the process that allows optimum conditions to be regulated in the body. This regulation of the internal environment must be independent of external environmental constraints. In humans this process is controlled by almost all of the bodily systems but mainly by the endocrine, respiratory and renal systems. Homeostasis therefore allows an organism to live in habitats that aren't ideally suited to the internal environment. (As only in favourable conditions will the organism thrive). This allows the organism to in an environment not best suited to it's internal functioning but in conditions which may be favourable for foraging etc. a prime example are fish, a fresh water fish lives in an environment which in definition is more dilute than it's internal environment, sea water fish on the other hand live in a environment where its surroundings are more alkali than its internal environment.

The need for homeostasis can be 'traced' to the cellular level, as cells interact with their immediate environment (either via cellular communication, signal proteins, expulsion of ion, uptake of ions). It is this communication, which ultimately leads to a change in the external environment. Right to the organ level or tissue organisation were for example the expulsion of urea changes the blood pH and osmolarity. These internal changes are countered by the excretion of hormones etc, (these substances share 4 main structural forms. Amines, steroids, prostalglandin and peptides) which start a 'chain reaction' to nullify the change these hormones are either secreted via ducts (exocrine system) or directly into the blood stream, (endocrine system).
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Homeostasis therefore is controlled by many systems, and although complex, many multi organ physiological mechanisms help regulate in many ways. However the theory of an internal environment wasn't recognised until a French physiologist Claude Bernard in 1872 put forward the idea of a constant internal environment stating, 1"Constancy of the internal environment is the condition of free life".

It is however important to remember that the regulation of an internal environment does not only concern body temperature but also such things as blood pH [H+], Blood glucose concentration, osmotic potential etc. All of these systems must be ...

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