Changes

*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.