Provide an example of maintaining homeostasis at the system level.

An example of homeostasis is blood sugar level. When the blood sugar level is very high, the pancreas produces insulin, and insulin tells the cells to take the glucose and use it. If cells need energy, they make the cell respiration and produce energy. If they don't need it, they convert it into glucogene or fat and store it. On the contrary, when the blood sugar level is very low, pancreas produce glucagon, which tells cells the opposite: make glucose appear! So if they don't have glucose, they convert glucagon or fat into glucose and release it into the blood.