 Fig.1. Homeostasis is maintaining a balanced internal environment.. ° Life originated in water. The reptiles, mammals, and birds evolved from the adventurous creatures that migrated into an aerial environment. These animals have developed very efficient body structures and miraculous physiological trends, yet every living cell in their bodies still has to be bathed in a liquid medium. Unlike in the sea the environmental conditions on land fluctuate much more. In spite of these changes, the ability to maintain the consistency of the body fluid has been termed ‘homeostasis’  . Homeostasis of Temperature Animals capable of temperature regulation are called homotherms. They achieve this by taking corrective action. [Such actions are called negative feed back.] Heres how they do it.  The hypothalamus acts as a receptor in regulation, by detecting changes in body temperature. [These receptors are better known as thermo-receptors.)
Corrective actions to lose heat. [Negative feed back]
Actions to conserve heat [This is also negative feed back.]
Fig.2. A man need not worry. 1. Homeostasis of Temperature. The average temperature of a human being is 37° C. It is quite normal to fluctuate it between 35°. and 38°. The body can make adjustments to lower it from a maximum of 41. Once these limits are passed there can be positive feedbacks that can lead to death.
Positive Feed back These actions will make things worse. A temperature above 41. or below 35 will induce positive feed backs. A high temperature will produce a higher rate of metabolism which will further increase the temperature and even cause the death. Lowering of temperature excessively will make metabolism almost impossible and cause the condition known as hypothermia. Fight or Flight …..A positive feed back In emergencies, adrenaline is released by the body to fight or 'flight reactions'. Adrenaline is secreted by the adrenal glands. The secretion of it leads to increased metabolism, breathing and heart rate. Once the emergency is over, and adrenaline levels drop, the homeostatic controls prevail. 2. Homeostasis of Water …Osmoregulation Osmoregulation is the regulation of water concentrations in the bloodstream, effectively controlling the amount of water available for cells to absorb. Osmoreceptors that are capable of detecting water concentration are situated on the hypothalamus.
 Pancreas Receptors The receptors of the pancreas are responsible for monitoring glucose levels in the blood, since it is important in every cell for respiration. Two types of cell release two different hormones from the pancreas, insulin and glucagon. These hormones target the liver, one or the other depending on the glucose concentration
The Liver The liver acts as a storehouse for glycogen, the storage form of glucose. When either of the above hormones target the liver, the following occurs
Diabetes insipidus is a condition where excess urine is excreted caused by the sufferers inability to produce ADH and promote the retention of water. Diabetes Mellitus is another form of diabetes where the sufferer does not have the ability to produce sufficient insulin, meaning that glucose cannot be converted into glycogen. Anyone who has this condition usually has to take injections of insulin after meals and snacks to maintain their storage of glucose needed in emergencies.  Question 1.0 1. What is the mass of glucose on 100cm3 of normal blood? 2. What can make the normal blood sugar level to increase in a healthy person? 3. What is the hormone, secreted by pancreas, that can bring about a negative feed back when the glucose level rises? 4. What is the expected negative response when fasting? 5. Name the product formed as a result of the above negative response.  Question 2.0
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