Adrenaline and secondary messengers

• The pancreas is an organ that produces insulin, glucagon, somatostatin, and digestive enzymes.
• Insulin lowers blood sugar levels by promoting the uptake of glucose into cells where it can be used as energy or stored as glycogen.
• Glucagon raises blood sugar levels by stimulating the liver to convert glycogen back into glucose and release it into the bloodstream.
• Some hormones are proteins , although they act as chemical messengers for the endocrine system, they have to bind to receptors on target cells because they are not lipid soluble.
• Some hormones have to rely on secondary messengers to work inside the cells and amplify the original signal from the hormone binding receptor
• Glucagon and Adrenaline rely on secondary messengers.
• With glucagon (glycogenolysis) :

  1. Glucagon binds to liver cell membrane receptors
  2. G protein is activated which activates the enzyme adenylyl cyclase (AC) by changing its shape.
  3. Active AC converts ATP to cyclic AMP (cAMP)
  4. cAMP is the second messenger that initiates a protein kinases
  5. Protein kinase enzyme activate a cascade which catalyzes the breakdown of glycogen to glucose.
• Non-steroid hormones require secondary messengers to activate their target cells.
• Adrenaline is released from the adrenal glands , on top of the kidneys
• if there is a low concentration of blood glucose then adrenaline is secreted but also when stressed or excising.
• With adrenaline (glycogenolysis):

  1. Adrenaline is a hormone which binds to different receptor cells on liver cells to glucagon
  2. the causes enzyme AC to change shape and become activated
  3. Active AC catalyzes the conversion of ATP to cyclic AMP
  4. cAMP initiates a protein kinases
  5. Protein kinase enzymes activate a cascade which catalyzes the breakdown of glycogen to glucose.
• Adrenaline:

  • activates glycogenolysis but also inhibits glycogenesis
  • Activates glucagon secretion and inhibits insulin secretion from the pancreas to make sure glucose concentrations in the blood increase
  • stimulates breakdown of glycogen stores in muscles in exercise
  • the glucose produce remains in the muscle cells where it is needed for respiration
  • preparing flight or fight response