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September 12, 2011

Merriam-Webster defines homeostasis as a relatively stable state of equilibrium or a tendency toward such a state between the different but interdependent elements or groups of elements of an organism, population, or group.

I define homeostasis as the ability of organism to maintain a stable internal environment to survive. Homeostasis is made up of many other systems. These include the digestive, respiratory, cardiovascular, and urinary systems. All of these systems include three main components: receptors, effectors, and a control center. Together these three components work together to keep the body in a stable internal environment.

The receptors are what sense that a change is occurring inside the internal environment and sends that information to the control center. The control center is basically the brain and determines what to do to bring the internal environment back to normal. It then proceeds to instruct the effectors what actions to take to in order to stabilize the environment. In the human body the receptors are usually molecules or cells that sense stimulus and send information to the control center. The control center then instructs muscles or glands to fix the problem.

The effectors fix the problem by either enhancing it (positive feedback) or depressing it (negative feedback). Negative feedback is the most common type of feedback. A good example of negative feedback is the regulation of glucose in the blood. After a meal the levels of glucose in the blood usually increase and once this happens the cells in the pancreas detect the change and signal to the pancreas to bring the levels back down to normal. The pancreas then reads the signals and gives out insulin to bring the levels of glucose in the blood back to normal.

Positive feedback is usually a bad thing for a person because it produces unstable conditions. However, when it comes to blood clotting positive feedback is what helps minimize the bleeding. This works in a relatively simple way. Platelets, which are cellular elements recognize that their is a bleeding problem. Once they recognize this a chemical reaction takes place that causes them to become sticky. Next they adhere to the wall of the blood vessel that has been punctured. More and more platelets come until the blood vessel is fully clotted.

Before I researched homeostasis I had no clue what it was. After reading through chapter one of Hole’s Human Anatomy & Physiology I can happily say I now understand it completely. Homeostasis is a very simple ability humans and other organisms have that help keep them alive. Without it we would be doomed!

*Information and pictures from Hole’s Human Anatomy & Physiology and lecture notes

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