Neural Control of the Pancreas

The pancreas plays a critical role in the control of nutritional homeostasis. It consists of two major parts, the exocrine pancreas, which releases digestive enzymes; and the endocrine pancreas, which releases hormones such as insulin, glucagon, pancreatic polypeptide and somatostatin and maintains glucose homeostasis. Cells in the endocrine pancreas are organized in pancreatic clusters of cells, the islets of Langerhans. Within the islets, the β-cells, which secrete insulin, are the predominant cell type and comprise approximately 70% of the cells within the islets. The remaining cells consist of α-cells that secrete glucagon, δ-cells that secrete somatostatin, and cells that secrete pancreatic polypeptide. The main function of the exocrine pancreas is to aid in digestion by secreting digestive enzymes and bicarbonate into the duodenum. The exocrine pancreas consists of only two major cell types, namely acinar cells that synthesize, store and secrete digestive enzymes; and ductal cells that secrete chloride and bicarbonate. Both parts of the pancreas are innervated by the sympathetic and parasympathetic nervous system, with separate pathways regulating the exocrine and the exocrine pancreas. In this chapter, we provide an overview of the central neural pathways that control the pancreas and the main neurotransmitters expressed in these pathways.