Regulating Blood Glucose

• Endocrine Glands

  • Produce and secrete hormones (chemical messengers) directly into the blood.
  • E.g. Pancreas secretes insulin
• Exocrine Glands

  • Produces and secretes extracellular secretions into ducts
  • E.g. Tears into tear ducts and Salivary glands secrete salivary amylase
• The pancres is a multifunctional organ that releases pancreatic enzymes into the small intestine - Protease, amylase and lipase, via a duct (exocrine)
• Islets of Langerhans produce hormones

  • Alpha cells produce glucagon
  • Beta cells produce insulin

  Released directly into the blood so endocrine.
• Glucose concerntrations in the blood rise so glucose diffuses into islets of langerhan cells as concerntrations increase the release of insulin is triggered.
• Blood glucose is maintained at 90mg/100ml. When blood glucose gets too low and the cells are starved of repiratory substrate, it is called hypoglycaemia.
• Blood glucose is maintained at 90mg/100ml. If this gets too high and water potential of the blood is too low, it is called hyperglycaemia
• Glucose can come directly or be stored as glycogen in muscles and liver to be broken down into glucose or be made for glycerol and amino acids.
• The balance of blood glucose is regulated by insulin, glucagon and adrenaline.
• Glycogenolysis - The breakdown of glycogen into glucose
• Glycogenesis - Conversion of glucose into glycogen.
• Gluconeogenesis - Synthesis of a new glucose
• Lipogenesis - Synthesis of new fats
• All cells, apart from RBC, have an insulin receptor.
• The binding of insulin causes conformational change in insulin receptor which causes more glucose carriers to be inserted into the membrane.
• If respiratory needs are met liver and muscle cells convert glucose to glycogen - Glycogenesis
• If glycogen stores are adequate glucose is converted into fat in the liver and adipose tissue - Lipogensis
• Insulin and glucagon work in opposition - they are antagonists which can cause negative feedback.