...And how it works with other systems.

Fun fact about homeostasis

The concept of homeostasis is widely used, in physiology and psychology, to identify what seems to be a general attribute of living organisms: the tendency to maintain and restore certain steady states or conditions of the organism. An obvious example is that of body temperature, which in the human tends to fluctuate only in a narrow range about the value 98.6° F. When the temperature rises above the normal range, corrective reflexes (perspiration, reduced metabolism, etc.) go into action to restore the steady state. Persistent deviation may initiate other actions (moving into the shade, plunging into water, etc.). If body temperature drops, other corrective actions are observed.http://www.encyclopedia.com/topic/Homeostasis.aspx

Why junk food is bad for you

Junk food is food that is calorie-dense and nutrient poor. In recent decades, junk food, fast food and convenience food consumption in the United States have increased dramatically, with 25 percent of people now consuming predominantly junk food diets. This trend has occurred concurrently with rising epidemics of numerous chronic diseases and accounts for a long list of reasons why eating junk food is bad. http://healthyeating.sfgate.com/reasons-eating-junk-food-not-good-3364.html