What is homeostasis?

The maintainance of a constant internal environment in organisms- mantaining the chemical make up, volume and other features of the blood and tissue fluid within restricted limits. It ensures that the cells are in an envirnment that meets their needs and allows them to function properly . There are changes but they are all around a fixed point- homeostasis is the ability to return to that set point.

The importance of homeostasis

  • Enzymes are sensitive to changes in pH and temperature. Any change to these factors reduces the efficiency of the enzymes and may prevent them from working all together, by denaturing them
  • Changes to the water potential of the blood can cause cells to shrink and expand as a result of water leaving or entering them by osmosis. The maintainance of a contant blood glucose concentration is essential in ensuring a constant water potential- it also ensures a reliable source of glucose for respiration by cells.
  • Organisms with the ability to maintain a constant internal envirnment are more indepedant of the external envirnment. This means that they have a larger geopraphical range and therefore have a greater chance of finding food.

Control mechanisms

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

  • the set point- this is the desired level, or the norm, at which the system operates
  • receptor- this detects any deviation from the set point and informs the...
  • controller- this coordinates information from various receptors and sends instuctions to the relevent...
  • effector- which brings about the changes needed to return the system to the set point. This return to normality creares a 
  • feedback loop- which informs the receptor of the changes to the system brought about by the effector

Coordination of control mechanisms

  • systems normally have more than one receptor and effector- this is important to ensure that the information provided by receptors is analysed by the control centre before action is taken
  • For example- during exercise temperature receptors on the skin by detect a decrease in temperature (due to sweating), and signal that body temperature needs to be raised, however there will be a rise in blood temperature. The brain analyses this information, which in this case is to not raise the body temperature and so vasodilation is most likely to occur.

Regulation of body temperature

Mechanisms of heat loss and gain

Methods of gaining heat include:

  • production of heat- metabolism of food during respiration
  • gain of heat from the enviroment- by conduction, convection and radiation

Methods of losing heat include:

  • evaporation of water- sweating
  • loss of heat to the envirnment- by conduction, convection and radiation

Terms explained:

  • Conduction- transfer of energy through matter from particle to particle. Heat causes the atoms to vibrate and gain kenetic energy- this causes adjecent particles to do the same
  • Convection- transfer in heat as a result of the movement of the warmed matter itself
  • Radiation- electromagnetic waves hit an object causing it to heat up



No comments have yet been made