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Principles of homeostasis

  • Homeostasis is the maintainance of a constant internal environment.
  • Homeostasis works by negative feedback; this means any deviation from the norm is detected, and corrective mechainisms bring it back to its norm.
  • The internal environment is made up of tissue fluids that bathe each cell, supplying nutrients and removing wastes.
  • Maintaining the featurs of this fluid at the optimum levels protects the cells from changes in the external environment, thereby giving the organism a degree of independence.

What it homeostasis?

  • Homeostasis is the maintenance of a constant internal environment in organisms.
  • It involves maintaining the chemical make-up, volume and other features of blood and tissue fluids within restricted limits.
  • Homeostasis ensures that cells of the body are in an environment that meets their needs and allows them to function normally despite external changes.
  • There are constant fluctuations brough about by variations in internal and external conditions, e.g. changes in temperature, PH and water potential.
  • However, these changes occur around a set point and so maintain organisms balanced equilibrium.

The importance of homeostasis

Homeostasis is essential for the proper functioning of organisms for the following reasons:

  • Body temperature and PH - because enzymes and other proteins, such as channel proteins, within cells, are sensitive to temperature and PH changes. A slight change alters the enzymes/proteins tertiary structure, causing them to change from their original shape, and function less adequately. If the change in PH and temperature becomes so large they eventually denature altogether.
  • Water potential and blood glucose levels - maintining this prevents cells shrinking or expanding due to osmotic gain or exit. As a consequence cells will not operate normally.
  • It also increases the range of habitats available for organisms to survive.

Control mechainisms

The control of any self-regulating system involves a series of stages that feature:

  • The set point/input, which is the desired level, or norm, at which the system operates. This is monitered by...
  • receptor, which detects any deviation from the norma and informs the....
  • controller, which coordinates information from various receptors and sends instructions to the appropiate....
  • effector, which brings about the changes needed to resurn the system to the set point. This return normally creates a....
  • feedback loop/output, which informs the receptor of the changes to the system brough about by the effector.

Regulation of body temperature

  • If an organisms body temperature is too low, the rate at which enzyme controlled reactions take place may bee too slow for the organism to function properly.
  • On the other hand, if the body temperature is too high, enzymes may be denatured and the organisms may cease to function altogether.
  • Therefore animals need to regulate their body temperature; this is a process call thermoregulation.

Mechainisms of heat loss and gain

  • Methods of gainaing heat include:
  • Production of heat by metabolism of food during respiration.
  • Gain of heat from the environment, by conduction (e.g. from the ground), convection (e.g from surrounding air or water), and radiation.
  • Methods of losing heat include:
  • Evaporation of water, e.g. through


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