Pancreas

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The Pancreas is an elongated structure that lies behind the stomach. It produces and secretes both insulin and glucagon. These hormones control sugar metabolism.

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The endocrine functions of the pancreas are contributed by the islets of Langerhans, small "islands" of cells composed of three separate cell types. Alpha cells secrete the hormone glucagon, which elevates glucose levels in the blood. Beta cells secrete insulin, which affects the metabolism of proteins, carbohydrates, and fats. Delta cells secrete somatostatin, which seems to inhibit the release of both glucagon and insulin. When these hormones are secreted in excessive or limited amounts, the level of glucose available for energy in the brain may be profoundly affected. Glucose is the primary source of energy in the central nervous system. Low levels of blood glucose, hypoglycemia, can occur in response to excessive levels of insulin. Insulin allows glucose to enter neurons for energy production, and when in excess, may deplete blood levels. Prolonged hypoglycemia leads to cerebral dysfunction, including mental confusion, hallucinations, convulsions, and eventually coma. Epinephrine is also released by the adrenal medulla in hypoglycemic conditions, inducing increased heart rate, blood pressure, sweating, and anxiety. High levels of blood glucose can occur when levels of insulin are low as in diabetes mellitus. If not corrected rapidly, the person will often slip into a deep coma due to the suppression of brain metabolism. A sensitive balance of glucose within the blood stream and within neurons must be maintained for optimal physiological and behavioral functioning.