Living organisms especially, mammals and birds (with few exceptions), tend to maintain a stable state by maintaining a constant internal environment. These animals are also known as endothermic animals. This phenomenon of regulation is known as homeostasis.
On the other hand ectothermic animals like reptiles, insects, amphibians, arachnids and fish show certain behavioral adaptations to regulate their internal conditions. For example, reptiles raise their body temperature in the morning by resting on sun-heated rocks.
Mammals and birds can maintain a constant body temperature and hence are known as warm blooded creatures. During the cold season these animals convert food into energy. On the other hand, cold blooded animals become sluggish in cold conditions and often go into hibernation. Homeostasis is responsible for regulation of many other factors like, constant blood pH, blood glucose, salt and water concentration etc. In many cases homeostatic regulation is controlled by the release of hormones into blood.
However processes like simple diffusion also help to maintain a proper balance
Maintenance of constant water and glucose levels are done in the following ways- An increase in water concentration within the body is sensed by certain osmoreceptors situated on the hypothalamus. The chemical message is sent from the hypothalamus to the pituitary gland which secretes ADH hormone. The anti-diuretic hormone acts on the kidneys affecting the permeability of the tubules. This in turn regulates the water levels within the body.
Blood glucose levels are maintained at constant levels within the body with the help of hormones like Insulin and Glucagon. Both of these hormones are secreted by the pancreas and these hormones target the liver. A higher levels of glucose in the blood stimulates a higher secretion of insulin and a lesser secretion of glucagon and when the levels of glucose is lesser in blood, the levels of secretion of both the hormones are reversed. The liver in turn either facilitates the conversion of glucose to glycogen or allows the breakdown of glycogen to glucose units.
Feed Back Mechanism in Animals
A feed back mechanism controls the regulation within the body and is made up of three interdependent components. The changes in the environment are sensed and recorded by the receptors. The stimulus is sent from the receptor to the control centre which is generally the brain. The control centre generates a response to the stimulus and sends the signal to the effectors which are organs like muscles. After the effector organs receive the stimulus from the control centre they can show an enhanced change in positive feedback mechanism or a depressed change in case of negative feedback mechanism.
Any disturbance to homeostasis disturbs the internal environment and leads to various diseases. Diseases like diabetes, hypoglycemia, dehydration, gout etc are the net result of homeostatic imbalance.