Homeostasis translates roughly from Greek, meaning ‘to stand equally', coined by Walter Bradford Cannon who detailed the term in his book ‘The Wisdom of the Body', although the concept was initially studied by Claude Bernard. It is the process in all living organisms that controls an internal environment, in order to keep it stable.
Homeostasis uses hormones to control body conditions. This is vital for the body's survival, because the chemical reactions taking place are easily imbalanced so it is necessary to both monitor and control the conditions.
Temperature control is one of the most important parts of homeostasis - the body must be kept at around 37 degrees. If the temperature rises above this the enzymes that speed up reactions in our body will begin to denature - a sort of warping of the shape that means it is unable to break down long chain molecules. If the temperature drops below 37 degrees then the enzymes will not be at the optimum conditions for their use, and slow down.
The brain monitors the body through the thermoregulatory centre, which controls the response if body temperature fluctuates. If the temperature is to low then vasoconstriction takes place. The capillaries near the surface of the skin shrink, preventing heat loss from the blood through the skin to the air. The muscles also contract and relax rapidly, known as ‘shivering' - this generates heat as respiration takes place more rapidly inside the muscle cells, and a by-product of this is heat. The hairs on the skin also rise, causing bumps, known as ‘goose pimples', trapping air against the skin, creating an insulating layer against the cooler air.
If the body is too hot, the reverse takes place. Vasodilatation allows heat to be lost to the air as the body's capillaries expand, bringing blood to the surface of the skin - this is also why we flush red when hot. Hairs on the skin lie flat; to prevent any trapped air from insulating the body and hence heating it. Sweat is produced on the surface of the skin, which then evaporates off cooling the skin - however this does take a lot of useful fluids the body needs.
To keep homeostasis, the body also has to keep its ion, water and glucose levels balanced. The control of water is known as ‘Osmoregulation'. If the water level in the blood is too high then the excess is added to the urine. If it is too low, then water is reabsorbed from the Kidneys. This process is the same for ions.
Glucose is a different matter, as many diabetics will know. If there is too little glucose in the bloodstream, the body uses the hormone glucagon to convert stores of glycogen into glucose for use in respiration. If there is too much glucose in the blood then insulin in secreted from the pancreas and this converts the glucose into glycogen, which is stored in the liver. Types one and two diabetics have problems with insulin production, so in their bodies the glucose builds up in the bloodstream, which can potentially kill the sufferer without regular injections of insulin
