Neural mechanisms in the control of blood glucose concentration.

Recent studies of sensory signals from the visceral areas have enhanced our understanding of mechanisms that control blood glucose levels. The activity of efferent fibers to the pancreas, liver, and adrenal medulla is modulated by both central glucose-responsive neurons and peripheral (gustatory, intestinal and hepatic) glucose sensors. It is well known that induction of hyperglycemia facilitates efferent activity of the pancreatic and hepatic branches of the vagus nerve. This in turn increases insulin secretion from the pancreas and glycogen synthesis in the liver. Hypoglycemia activates efferent activity of the pancreatic, hepatic and adrenal branches of the splanchnic nerve, and this results in increased glucagon secretion from the pancreas, release of glucose from the liver and secretion of catecholamines from the adrenal medulla. Glucose-responsive neurons in the hypothalamus and medulla oblongata may be involved in the modulation of this autonomic efferent activity.