The document discusses hormonal communication and the control of blood glucose concentration. It focuses on the pancreas, which is both an exocrine and endocrine gland. The pancreas' exocrine role is to secrete pancreatic juices into the duodenum. Its endocrine role is carried out by the islets of Langerhans, which contain alpha and beta cells. Alpha cells secrete glucagon to stimulate glucose release, while beta cells secrete insulin to stimulate glucose uptake. The pancreas detects changes in blood glucose and releases the appropriate hormone, insulin or glucagon, to regulate glucose levels.