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Homeostasis is the ability of the body to keep a stable internal environment through different self-regulating mechanisms. These include positive feedback mechanisms and negative feedback mechanisms, as well as the three basic components for regulating homeostasis: receptors, the control center and effectors. With these three homeostatic control mechanisms, positive feedback and negative feedback work toward creating homeostasis.
Negative feedback is a homeostatic control mechanism that notices a variable in the body that has deviated from its set point and helps return it back to its original state. For example, when one becomes stressed or excited, his or her blood pressure rises. One's blood pressure is the variable that has deviated, or moved, from a normal blood pressure level to a higher blood pressure level. The normal blood pressure level is the set point, and negative feedback helps in blood pressure regulation by using the three components of homeostasis.
The first component are receptors. Receptors receive messages about a change in the internal environment. In this case, the receptors are located in the blood vessels, which receive information that the blood pressure has risen out of its normal range. Receptors are needed in order to determine what is happening within the body and for them to send these messages to the control center.
The control center decides what a particular value should be within the body. In this example, the control center, which is the brain, determines what a normal blood pressure should be. The brain receives the message from the receptors that a change has occurred in the body and that action needs to be taken to maintain homeostasis. The brain then sends the correct set point of blood pressure to the effectors.
The effectors are muscles or organs that receive messages from the control center about what the correct set point should be. The effectors then correct the deviation or change by following the orders of the control center. With blood pressure, the effectors in the body will receive the correct set point for blood pressure from the brain and will correct the deviation by bringing down the blood pressure.
Positive feedback homeostatic control mechanisms are the opposite of negative feedback mechanisms, and they occur rarely in the body. Positive feedback notices a deviation from the set point and pushes that variable even further away from homeostasis. An example of positive feedback is the process of blood clotting.
When one suffers a cut and bleeds, blood platelets form and keep forming in order to stop the bleeding. The continuous clotting of platelets is positive feedback. It is positive feedback because it keeps increasing and growing away from a normal set point rather than decreasing and returning back to the original set point, as it would with negative feedback.