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Homeostasis

Homeostasis is the control of internal conditions, be it temperature, specific blood conditions or other variables within living organisms. The term ‘Homeostasis’ was first defined by the French physiologist, Claude Bernard, in 1865.

The purpose of homeostasis is to provide a consistent internal environment for set processes to occur. Each process, or reaction, has a desirable peak environment called the norm. Influences, such as an external influence, can cause deviation away from this norm level and the body will correct this change – this is called negative feedback.

Examples of negative feedback:

  • When blood pressure rises the heart will slow.
  • If glucose levels are too high the pancreas secretes insulin to stimulate the absorption of glucose.

Negative feedback is the most common type of reaction, because it is only natural to rectify a potential problem, but there is also positive feedback. This is when the body will push itself further away from the norm level. An example of this:

  • During hypothermia – if a human’s body temperature falls and is being lost quicker than it can be produced the metabolic rate will also drop. This causes a positive feedback and the body temperature will fall further from the norm.

Temperature Control

Many of the body’s enzymes are sensitive to temperature change, even by a few degrees difference, which then affects their reactions. This is because humans are endotherms, or warm blooded creatures, and are depend on creating their own heat.

Ways to change temperature:

  • Radiation – The transfer of heat between two objects through the air.
  • Conduction – The transfer of heat from direct contact between two objects.
  • Convection – The transfer of heat through moving air.
  • Evaporation – The loss of heat (and energy) through changing a liquid into a vapour.

The hypothalamus, located in the central brain, controls body temperature, hunger & thirst and sleep. It regulates body temperature by detecting change in blood temperature and sending relevant signals through the nervous system to the body’s organs to rectify this.

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