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HOMEOSTASIS
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Regulation - It's All About Homeostasis
Homeostasis is a term that is used to both describe the survival of organisms in an ecosystem and to describe the successful survival of cells inside of an organism. Organisms and populations can maintain homeostasis in an environment when they have a steady level of births and deaths. It is similar to the idea of equilibrium.
When discussing the internal workings of an organism, homeostasis describes an environment that supports the survival of cells. All of your body's systems work together maintain homeostasis inside of your body. Homeostasis is achieved by making sure the temperature, pH (acidity), and oxygen levels
(and many other factors) are set just right for your cells to survive. Homeostasis levels are different for each species.
Negative Feedback
Negative feedback is a process that happens when your systems need to slow down or completely stop a process that is happening. When you eat, food travels into your stomach, and digestion begins. You don't need your stomach working if you aren't eating. The digestive system works with a series of hormones and nervous impulses to stop and start the secretion of acids in your stomach. Another example of negative feedback occurs when your body's temperature begins to rise and a negative feedback response works to counteract and stop the rise in temperature. Sweating is a good example of negative feedback.

Positive Feedback
Positive feedback is the opposite of negative feedback in that encourages aphysiological process or amplifies the action of a system. Positive feedback is a cyclic process that can continue to amplify your body's response to a stimulus until a negative feedback response takes over. An example of positive feedback also can happen in your stomach. Your stomach normally secretes a compound called pepsinogen that is an inactive enzyme. As your body converts pepsinogen to the enzyme pepsin, it triggers a process that helps convert other pepsinogen molecules to pepsin. This cascade effect occurs and soon your stomach has enough pepsin molecules to digest proteins.
Body Temperature Example
A good example of system regulation of your body can be found in the regulation of body temperatures. You are a homoeothermic organism, which means you regulate your own body temperature. Other species like reptiles are not homoeothermic. Anyway, if your body gets too cold, a series of actions are taken to warm your body. Sensors throughout your nervous system can recognize when the temperature drops and might trigger your muscular system to start shivering. The constant contractions of your muscles allow heat to be generated. Your nervous and endocrine systems may also contract the blood vessels of your circulatory system to keep blood in the core of your body and not the extremities (like fingers).

Many advanced animals have muscular systems. You know you do. Did you know that your muscular system is made up of three different types of muscular tissue? You have smooth, cardiac, and voluntary muscle tissue in your body. Smooth muscle is muscle you rarely control such as the muscle in your intestinal tract. Cardiac muscle is very specific tissue found in your heart.
Voluntary muscle is the muscle that helps you move. All of those tissues add up to a muscular system that is found through your body. There is more to the muscular system than the muscles that help you move.
What Does This System Do?
The big purpose of the muscles found in your body is movement.
We could be talking about the movement of your legs while you walk. We could be talking about the beating of your heart. We could also be talking about the contraction of a very small blood vessel in your brain.
You have no control over most of the muscular system. You do control the voluntary muscle in your arms, legs, neck, and torso.
You have little or no control over the heart or smooth muscle.
Those other muscles are under the control of the autonomic
nervous system (ANS).
Interacting with Other Systems
We just teased the fact that your muscular system is closely connected to the nervous system. That makes sense since you usually have to think before you can move. Even though thinking is not always involved, the neurons of the nervous system are connected to most of the cells in your muscular system. You have smooth muscles that line your digestive system and help move food through your intestines. Smooth muscle also surrounds your circulatory system and lymph system. Those muscle tissues are spread throughout your body and are even involved in controlling the temperature of your body.