Whats involved in Homeostasis.

This is how receptors in the body detect a change in the level of an interior factor. This then activates effectors to restore the body to the optimum level.

We know that temperature and pH have 2 be kept constant, but the following features of the blood and tissue fluid also need to be kept within limits:

* Concentration of important ions such as potassium and calcium

* The Glucose concentration

* Water Potential

The Glucose concentration in the blood needs to be monitored closely because certain parts of the body can't store carbohydrates. So when there is a lack of glucose in the blood the area may malfunction.

The three sources of blood glucose are:

* Digestion of carbohydrates in the diet

* Breakdown of glycogen

* Conversion of none-carbohydrate compounds

The pancreas plays a large part in controlling the glucose levels. It contains cells which are sensitive to glucose concentration in the blood. It then produces either insulin when the concentration is to high, or glucagon if the levels get to low.

Insulin does this by activating enzymes that convert glucose to glycogen, and others, which promote the synthesis of fat.

Glucagon activates enzymes in the liver which are responsible for converting glycogen to glucose. It also stimulates the formation of glucose from other substances such as amino acids. These then pass out the cell and into the blood, raising the glucose levels.

Sometimes the pancreas can become diseased and fail to carry out functions such as secreting insulin. This will obviously effect the level of control over blood glucose levels, resulting in a condition called diabetes mellitus.

There are two types of diabetes mellitus:

* Type 1 or insulin dependent

* Type 2 or insulin independent

Another part of homeostasis in temperature control, different organisms control their temperature in different ways. Ectothermic organisms control their bodies' temperature by changing their behaviour. Birds and mammals are the only animals which do not do this.

Examples of how they do this is moving into shade, having darker outer colours (absorbing more heat).

Endothermes are animals that can maintain a stable temperature by using both behavioural and physiological methods. Mammals and birds are examples of endothermes.

When humans get goosebumps it is an example of our behavioural method to reduce the loss of heat.

Physiological changes include how blood temperature can rise or fall when the hyperthalimus detects a change in temperature and allows the autonomic nervous system to act in the appropriate way.

Jamie Evans