Human Nutrition Carbohydrates Home Science YouTube Lecture Handouts Part 5

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Maintenance of Blood Glucose Levels

  • For the feeling of well-being, the brain & other nervous tissues are dependent on blood glucose for energy
    • Fasting Blood Glucose level = 80 to 100 mg/dl
    • Normal Blood Glucose level = 130 to 140 mg/dl
    • Low Blood Glucose level = 30 to 50 mg/dl
  • Hypoglycaemic conditions leads to the symptoms like fatigue, Light-headedness, Jitteriness, irritability, sweating, headaches, etc.
  • If the levels become even lower fainting, coma and even death ensue. Therefore, it՚s imperative to maintain the normal blood glucose levels.
  • Liver acts as a Traffic cop because Glucose Glycogen
  • As time lapses, body cells remove glucose from blood to use for energy and blood levels of glucose go down. The body maintains normal blood glucose levels even when there is no carbohydrate in the diet, by converting non-carbohydrate substances to glucose
  • Gluconeogenesis occurs in the liver and kidneys. During total starvation, gluconeogenesis is the chief mechanism by which blood glucose levels are maintained
Maintenance of Blood Glucose Levels
Supply of Glucose into The BloodHormonal ControlsRemoval of Glucose from The Blood
Sugars from the dietInsulinUtilised by cells for energy
GlycogenolysisGlucagonGlycogenesis
GluconeogenesisEpinephrine (Adrenaline)Lipogenesis
Pyruvic Acid Lactic Acid (Glycolytic Pathway)GlucocorticoidsSynthesis of numerous carbohydrate derivatives
-ThyroxineGlycolysis in RBC
-Growth HormoneElimination by Urine

Hormonal Control of Blood Sugar Levels

Insulin

  • Produced by the Beta - cells of islets of Langerhans in the pancreas
  • Also called as feasting hormone
  • Increases Glycogenesis & Lipogenesis

Glucagon

  • Produced by the Alpha - cells of islets of Langerhans in the pancreas
  • Acts opposite to insulin
  • Rises blood glucose level by glycogenolysis by activating the enzyme phosphorylase
  • It enhances the gluconeogenesis from amino acids and lactate

Epinephrine (Adrenaline)

  • It is a hormone secreted by the adrenal medulla
  • It favours the breakdown of liver and muscle glycogen to yield blood glucose (glycogenolysis) and decreases the release of insulin from the pancreas, thus raising blood sugar.
  • It is increased during anger/fear and the subsequent glucose formation provides extra energy for crisis response

Glucocorticoids

  • Steroid hormones elaborated by adrenal cortex
  • It reduces the glucose utilization in the extrahepatic tissue and also increase the rate at which protein is converted into glucose thus counteracting the action of insulin
  • It also enhances the uptake of amino acids by the liver and increase the activity of transaminases and other enzymes involved in the hepatic gluconeogenesis

Thyroxine

  • Severe lowering of blood glucose concentration increases thyroxine secretion
  • It enhances the action of epinephrine
  • It also increases the rate of hexose absorption from the intestine

Growth Hormone

  • This is elaborated by the anterior pituitary gland
  • This raises blood glucose level by increasing amino acid uptake and protein synthesis by all cells by diminishing cellular uptake and increasing the mobilisation of fat for energy.

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