glycogenolysis

Examples of glycogenolysis in the following topics:

• Insulin Secretion and Regulation of Glucagon

  • Glucagon is produced by alpha cells in the pancreas and elevates the concentration of glucose in the blood by promoting gluconeogenesis and glycogenolysis.
  • Liver cells have glucagon receptors and when glucagon binds the liver cells convert glycogen into individual glucose molecules and release them into the bloodstream, in a process known as glycogenolysis.

• Adrenergic Neurons and Receptors

  • Adrenaline or noradrenaline are receptor ligands to α1, α2 or βadrenergic receptors (the pathway is shown in ). α1 couples to Gq, which results in increased intracellular Ca2+ which results in smooth muscle contraction. α2, on the other hand, couples to Gi, which causes a decrease of cAMP activity, resulting in smooth muscle contraction. β receptors couple to Gs, and increases intracellular cAMP activity, resulting in heart muscle contraction, smooth muscle relaxation and glycogenolysis.
  • Further effects include glycogenolysis and gluconeogenesis from adipose tissue and liver, as well as secretion from sweat glands and Na+ reabsorption from kidney.
  • Adrenaline and noradrenaline are ligands to α1, α2, or β-adrenergic receptors. α1 receptors couple to Gq, resulting in increased intracellular Ca2+ and causing smooth muscle contraction. α2 receptors couple to Gi, causing a decrease in cAMP activity and resulting in smooth muscle contraction. β receptors couple to Gs, increasing intracellular cAMP activity and resulting in heart muscle contraction, smooth muscle relaxation and glycogenolysis.

• Epinephrine and Norepinephrine

  • Binding to α-adrenergic receptors inhibits insulin secretion by the pancreas, stimulates glycogenolysis (the breakdown of glycogen) in the liver and muscle, and stimulates glycolysis (the metabolic pathway that converts glucose into pyruvate) in muscle. β-Adrenergic receptor binding triggers glucagon secretion in the pancreas, increased adrenocorticotropic hormone (ACTH) secretion by the pituitary gland, and increased lipolysis by adipose tissue.

• Hormonal Regulation of Metabolism

  • Glucagon raises blood glucose levels, eliciting what is called a hyperglycemic effect, by stimulating the breakdown of glycogen to glucose in skeletal muscle cells and liver cells in a process called glycogenolysis.

• Carbohydrate Molecules

  • Whenever blood glucose levels decrease, glycogen is broken down to release glucose in a process known as glycogenolysis.

• Adjustments of the Infant at Birth

  • Plasma glucose is maintained by glycogenolysis.