The sugary snack you devour enters your digestive system and is broken down to simple sugars like glucose. Glucose enters the bloodstream, causing an increase in blood glucose levels. But various mechanisms bring blood glucose back down to its normal level, the set point. This is an example of homeostasis, the body’s tendency to maintain relatively constant internal conditions. Hormones produced by the pancreas regulate blood glucose levels. Let's zoom in. When blood glucose levels are high, glucose molecules leave the blood and enter beta cells in the pancreas. The beta cells respond by releasing the hormone insulin. Insulin enters the bloodstream and is transported to cells all over the body. Let's see what happens in the liver. Insulin binds to receptors on liver cells. This causes the cells to take in more glucose. Inside the liver cells, glucose is converted to glycogen, a storage molecule. Blood glucose levels decrease as glucose is taken up by liver cells and other body cells. As a result, less and less insulin is released by the pancreas, and blood glucose levels stabilize at their set point. This is an example of how negative feedback maintains homeostasis. What happens if you’ve skipped lunch, and your blood glucose levels are low? Let’s zoom into the pancreas again. When blood glucose levels are low, alpha cells in the pancreas release the hormone glucagon. Glucagon enters the bloodstream and acts on target cells in the liver. Glucagon binds to receptors on the liver cells, signaling the liver cells to break glycogen down to glucose. Glucose is released, and blood glucose levels increase. As a result, less glucagon is released by the pancreas, and blood glucose levels stabilize at their set point. In this way, two hormones with opposing effects allow the body to maintain homeostasis of blood glucose levels. In diabetes, the body is unable to maintain homeostasis of blood glucose levels. In type 1 diabetes, the beta cells of the pancreas are destroyed by the immune system, and so no insulin is produced. In type 2 diabetes, the pancreas produces insulin but target cells do not take up glucose. In both types of diabetes, when blood glucose levels rise, cells do not take up the additional glucose, and so blood glucose remains high. This example shows the importance of homeostasis in everyone's life. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings