Negative and Positive Feedback Systems - Homeostasis

Concentration Gradients and Homeostasis

Time to backup and talk about feedback systems that keep the concentration of things your body needs to function normally.

Homeostasis is a state reached when your chemicals necessary for life are within their normal concentration range.

Wide swings in concentrations is not good. You don't feel good when "wide swings" occur. Do you feel good with high concentrations of glucose in your blood that persist? No.

A "Negative Feedback System" , when operating normally, prevents "wide swings" in the concentration of substances that are important to your body systems. One of these chemicals is a by-product of digestion.

If the body produces glucose for the metabolism necessary for life in all our living cells there is a feedback system ( this link is a series of excellent diagrams of negative and positive feed back systems) for glucose that turns off the production of glucose when it is no longer needed. It does this to prevent the concentration of glucose to reach levels in the blood that are dangerous. The swing upward (wide swing) of glucose is too great if the feedback system isn't working.

Lets look at a muscle cell. If its contracting it needs food (glucose) to manufacture energy for contraction to occur. When the period of contraction ends the need for glucose ends. To conserve glucose for another time a process takes place to remove the excess glucose from the blood and store it. The normal level of glucose is maintained. Insulin does this normally.

Think of a small stone thrown into a quiet pond. Little waves are produced. This is very similar to the small up and down swings in your glucose concentration if the feedback system is working well. This is homeostasis. 

The process is called a "Negative Feedback System." It prevents "wide swings" in the concentration of necessary chemicals, like glucose, from occurring.   It starts a system up to provide the necessary chemical (glucose) and shuts down the process when the need for (glucose) temporarily disappears. The body likes to save essential chemicals for a later time.

For a diabetic, the pancreas is not producing enough insulin to bring the concentration of glucose back to normal levels after the need for the glucose ends. (like a muscle contracting.)

The Negative Feedback System for glucose homeostasis is not functioning. The excess glucose is not returning for the storage process after the "need event." This, in very simple terms, is Diabetes.

Let me digress a bit, before I get one of my headaches when I start to think to much! :):)

A Positive Feedback System is Blood Clotting. You want blood clotting to occur and keep occurring at  the site of a good, bleeding scratch or cut to form a scab to prevent further fluids and electrolytes from leaving the body too quickly and not under body control. Since there is not a need to lose body fluids and electrolytes in uncontrolled events (like a severe cut) this system works only one - a positive action to make a clot and scab formation possible.