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Pancreas - Anatomy & Physiology (view source)
Revision as of 11:43, 24 July 2008
, 11:43, 24 July 2008→Glucagon
*Glucagon secretion is stimulated under conditions of hypoglycaemia and inhibited under conditions of hyperglycaemia. Parasympathetic innervation via the vagus nerve also stimulates release of glucagon.
*Glucagon secretion is stimulated under conditions of hypoglycaemia and inhibited under conditions of hyperglycaemia. Parasympathetic innervation via the vagus nerve also stimulates release of glucagon.
*Glucagon has a ''catabolic'' effect on body reserves.
*Glucagon has a ''catabolic'' effect on body reserves.
*The main target tissue is the liver.
*The main target tissue is the [[Liver - Anatomy & Physiology|liver]].
**Here it acts primarily to increase the degradation of glycogen via glycogenolysis and to increase the synthesis of glucose from amino acids via gluconeogenesis.
**Here it acts primarily to increase the degradation of glycogen via glycogenolysis and to increase the synthesis of glucose from amino acids via gluconeogenesis.
***Glycogen regulates the reaction in glycolysis which converts phosphoenolpyruvate (PEP) to pyruvate. This reaction is catalysed by the enzyme '''pyruvate kinase''' and produces a molecule of ATP. Glucagon ''inactivates'' this enzyme by phosphorylation via protein kinase A (PKA).
***Glycogen regulates the reaction in glycolysis which converts phosphoenolpyruvate (PEP) to pyruvate. This reaction is catalysed by the enzyme '''pyruvate kinase''' and produces a molecule of ATP. Glucagon ''inactivates'' this enzyme by phosphorylation via protein kinase A (PKA).
**It increases the β oxidation of fatty acids to provide energy for gluconeogenesis.
**It increases the β oxidation of fatty acids to provide energy for gluconeogenesis.
*Glucagon also acts on other tissues, including adipose tissue where it increases the rate of lipolysis and, skeletal muscle where it increases the rate of protein catabolism.
*Glucagon also acts on other tissues, including adipose tissue where it increases the rate of lipolysis and, [[Muscles - Anatomy & Physiology|skeletal muscle]] where it increases the rate of protein catabolism.
*Glucagon reduces basal metabolic rate.
*Glucagon reduces basal metabolic rate.
*Glucagon predominates during fasting metabolism.
*Glucagon predominates during fasting metabolism.