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Introduction to Homeostasis

Human Biology (Year 12) - Homeostatic Control

Ben Whitten

What is homeostasis?

Homeostasis is the maintenance of a constant optimal internal environment. Our body cells work best at a particular temperature, when surrounded by fluid with a particular pH level, when given a constant supply of oxygen and glucose, and when wastes are constantly removed. All of these factors (including other optimum conditions for cell function) are key components of homeostasis.

Homeostatic mechanisms allow us to be independent of our external environment. For example, if you suddenly plunge into a cold swimming pool, the cells found in your brain, stomach, liver, heart and other external organs will continue to function normally despite the sudden change in external temperature. Somatic cells are all surrounded by fluid, the composition and temperature of which must be maintained within very narrow limits to allow for normal cell function.

Some key factors which must be regulated include:

  • Core body temperature

  • pH concentrations of dissolved substances

  • Concentration of glucose in the blood

  • Concentration of oxygen and CO2 in the blood and other body fluids

  • Blood pressure

  • Metabolic waste concentrations

There is a dynamic equilibrium in which the input and output of materials and energy are balanced. To maintain homeostasis, the body must be able to both sense deviations in the internal and external environment, and respond to these changes.The nervous system and the endocrine system are the main sensory and controlling body systems. In the case of homeostasis, they operate through feedback systems.

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