One way the body maintains homeostasis is through negative feedback mechanisms. In negative feedback systems the output shuts off original stimulus or reduces its intensity. This causes the variable to change in a direction opposite to that of its initial change, returning it to its "ideal" value. The body does this in several ways. One way the body does this is through regulating body temperature. This regulation of body temperature takes place in a part of the brain called the hypothalamus. Withdrawal reflex is another way the body maintains homeostasis. An example of this is when a hand is jerked away from a painful stimulus such as broken glass. The endocrine system also plays a major role in maintaining homeostasis. One example of hormonal negative feedback is the control of blood glucose levels by pancreatic hormones. It is important that blood sugar levels remain at around 90 milligrams of glucose per 100 milliliters of blood. If the body takes in too much sugar the blood sugar levels spike upward and disrupt homeostasis. The result of this is to stimulate the inslulin-producing cells of the pancreas. These cells respond by secreting insulin into the blood. Insulin is used to accelerate the uptake of glucose by most body cells. Blood sugar levels then return to normal and the stimulus for insulin release diminishes.

The second way the body maintains homeostasis is through positive feedback mechanisms. In positive feedback mechanisms, the result or response enhances the original stimulus so that the activity (output) is accelerated. It is called positive feedback because the mechanism advances in the same direction as the initial disturbance, causing the variable to deviate further from its original value or range. The two main uses of positive feedback mechanisms are enhancement of labor contractions during birth and blood clotting. During birth oxytocin, a hypothalamic hormone, intensifies labor contractions. Oxytocin causes the contractions to be more frequent and more powerful until the baby is born and then the oxytocin stimulus releases to stop the intensity. Blood clotting occurs when the lining of the blood vessel breaks and needs repairing. Platelets, or blood elements, instantly cling to the injured site and release chemicals attracting more platelets. The positive feedback rapidly attracting platelets forms a blood clot.

Maintaining Body Homeostasis

**It is very important for the human body to possess both, negative feedback mechanisms, as well as positive fededback mechanisms to maintain homeostasis.