# Homeostasis --- **Homeostasis** is the state of balance or [[equilibrium]] that an organism must maintain in every biological system in order to stay [[biology|alive]]. For many systems there are optimal ranges that the body keeps the system in, for example [[body temperature]], blood sugar, pH or gas levels, vitamin or [[mineral]] levels, [[blood pressure]], etc. In other words, homeostasis keeps the internal balance steady while the external elements is changing constantly. ## Set Point A person's **set point** is their "fulcrum" so to speak. This is the state that a person's body will try to achieve via homeostasis. So if a two people are in the same room, and one person's [[body temperature]] set point is higher than the others (and all other factors being equal) that person will still be warmer than the other person, whose set point is lower. ## Negative Feedback vs Positive Feedback **Negative feedback** is a mechanism where a counter balance is applied to a state that is working to deviate from homeostasis. For example, if you are in a hot environment your body will sweat and dilate the blood vessels to dump heat, but if you're in a cold environment you will shiver to generate heat and blood vessels will contract to conserve heat. ![[negative feedback.png]] **Negative feedback** works between three main components, the **receptor** (to realize the need for for a response), the **control center** (to determine the response), and the **effector** (to enact the response). **Positive feedback** is a much more infrequently (about 3 or so examples) used mechanism where the change in the system triggers an even *stronger* change in the same direction. Instead of working to counteract whatever is effecting the system, positive feedback amplifies it. For example, when a wound is in need of clotting, the presence of platelets triggers chemicals that attract *more* platelets. ___