After you eat a meal your blood glucose levels rise. Cells in the pancreas sense the increase in glucose and release insulin. Insulin binds to cell surface receptors that activate molecules inside the cell leading to the insertion of glucose transporters in the cell membrane and the transport of glucose from the extracellular space into the cell. This results in decreased in blood glucose levels. The decrease is sensed by the pancreatic cells and insulin release is stopped. What kind of system is represented by the series of events described above?