Insulin and Glucagon
Control of Blood Glucose One of the most important and tightly regulated responses in the human body is the concentration of blood glucose (blood sugar). Glucose is the major breakdown product of cellular metabolism. As such, it is required both as an energy source and as a source of carbon for making organic molecules. Blood glucose concentrations are regulated by negative feedback pathways that are modulated by two separate hormones: insulin and glucagon. Both of these hormones are produced in special cells called islet cells, or islets of Langerhans – are found in clusters throughout the pancreas. Islet cells make up a very small percentage of the pancreas (about 1-2%); the remainder of the organ is an exocrine gland producing digestive enzymes and bicarbonate ion. This tiny number of endocrine cells is exceedingly important. Each islet contains two kinds of cells: alpha cells, which produce glucagon, and beta cells, which produce insulin.
