What exactly is Homeostasis? What examples exist in living things?
The property of a system, whether living or non-living, to maintain its internal environment is known as Homeostasis. This is achieved by the use of sensors conected to feedback loops, which are also linked to control mechanisms. The overall process is to maintain a constant condition.
Examples in living things include
Regulation of
(i) amounts of water and minerals in the body. This occurs in the kidneys.
(ii) body temperature. This is mainly achieved by the skin.
(iii) blood glucose level. This is achieved by the liver and the insulin provided by the pancreas.
Removal of Metabolic Waste
Excretion is also a homeostasis process. This is achieved by organs such as the kidneys and lungs.
Types of Feedback
There exist two main types of feedback to which a system responds:
Negative feedback occurs when a system responds so that the direction of change is reversed. This process has a tendency to keep things constant, to keep things and it allows the maintenance of homeostasis. For example, when the body temperature changes, sensors in the skin (receptors) and the hypothalamus both detect a change. This detection has the response of triggering a command message from the brain. The effect of this command is to initiate the correct response so that the temperature returns to its previous level.
Positive feedback occurs when things start to go wrong, or become unstable. Homeostasis is not achieved by positive feedback. A positive feedback amplifies a change. The overall dynamics of this system is to result in the state of the system to move further and further from a required condition needed in Homeostasis.
Further reading:
http://www.s-cool.co.uk/gcse/biology/homeostasis/revise-it/what-is-homeostasis
https://en.wikipedia.org/wiki/Human_homeostasis
http://www.xtremepapers.com/revision/gcse/biology/homeostasis.php