{"id":5103,"date":"2025-11-26T22:55:57","date_gmt":"2025-11-27T03:55:57","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/?post_type=chapter&p=5103"},"modified":"2026-01-12T18:35:15","modified_gmt":"2026-01-12T23:35:15","slug":"the-role-of-glucagon-and-insulin-in-blood-glucose-homeostasis","status":"web-only","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/chapter\/the-role-of-glucagon-and-insulin-in-blood-glucose-homeostasis\/","title":{"raw":"9p6 The Role of Glucagon and Insulin in Blood Glucose Homeostasis","rendered":"9p6 The Role of Glucagon and Insulin in Blood Glucose Homeostasis"},"content":{"raw":"Blood Glucose Homeostasis<\/strong>\r\n

Pancreatic Hormones - Glucagon and Insulin:<\/strong><\/h1>\r\n
    \r\n \t
  • The pancreas produces\u00a0two main hormones<\/strong>\u00a0involved in regulating blood glucose:\r\n
      \r\n \t
    • Insulin<\/strong>\u00a0(produced by beta cells)<\/li>\r\n \t
    • Glucagon<\/strong>\u00a0(produced by alpha cells)<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n

      Post-Meal: Regulation of Blood Glucose<\/strong><\/h1>\r\nStep 1: Post-Meal Rise in Blood Glucose Levels<\/strong>\r\n
        \r\n \t
      • After eating, glucose enters the bloodstream, causing\u00a0blood glucose levels to rise<\/strong>.<\/li>\r\n \t
      • Elevated blood glucose\u00a0stimulates beta cells<\/strong>\u00a0in the pancreas to release insulin<\/strong>.<\/li>\r\n<\/ul>\r\n

        Role of Insulin<\/strong><\/h1>\r\n
          \r\n \t
        1. Insulin facilitates the transport of glucose<\/strong>\u00a0into the body's cells, by stimulating the insertion of GLUT4 glucose transporters<\/strong> into the cell membranes of the body\u2019s cells.\r\n
            \r\n \t
          • \r\n
              \r\n \t
            • Insulin<\/strong> binds to insulin receptors<\/strong> on cell membranes.<\/li>\r\n \t
            • Triggers GLUT 4<\/strong> vesicles<\/strong> to move to the membrane and insert.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
            • Cells are then able to uptake glucose from the bloodstream.\r\n
                \r\n \t
              • Glucose is water-soluble and need a membrane transporter to enter cells.<\/li>\r\n \t
              • Prevents\u00a0cell starvation<\/strong> in glucose, the vital energy source (required for ATP production)..<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
              • Insulin facilitates ATP production:\r\n
                  \r\n \t
                • Glucose<\/strong> is used by cells to generate ATP<\/strong> through:\r\n
                    \r\n \t
                  • Anaerobic cellular respiration<\/strong> (Glycolysis) in which Glucose \u2192 Pyruvate + 2 ATP<\/strong><\/li>\r\n \t
                  • Aerobic cellular respiration<\/strong> (Krebs\/Citric Acid\/Tricarboxylic Acid Cycle) and Electron Transport Chain in which Glucose is broken down to produce 30-32 ATP<\/strong><\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
                  • Without insulin, glucose remains in blood, leading to\u00a0hyperglycemia<\/strong>, and cells would be deprived of energy, impairing ATP production.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
                  • Insulin stimulates glycogenesis<\/strong> (glycogen synthesis) in liver<\/strong> and skeletal muscle<\/strong>.\r\n
                      \r\n \t
                    • Glycogen is a fuel storage molecule that can be broken down into glucose.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
                    • Insulin also promotes the uptake<\/strong> of amino acids<\/strong> and lipids<\/strong> by cells which supports\r\n
                        \r\n \t
                      • Supports protein synthesis,<\/strong> cellular growth<\/strong> and maintenance<\/strong> and healing<\/strong>\r\n
                          \r\n \t
                        • Insulin influences gene expression and growth regulation!<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
                        • Insulin additionally promotes triglyceride<\/strong> synthesis in adipocytes<\/strong> (for storage of lipids as triglycerides)<\/li>\r\n<\/ol>\r\nOutcome:<\/strong>\r\n\u2022 Blood glucose levels decrease back to normal, maintaining homeostasis.<\/strong>\r\n

                          Between Meals: Low Blood Glucose<\/strong><\/h1>\r\n
                            \r\n \t
                          • Blood glucose levels\u00a0drop<\/strong>\u00a0as cells use glucose for energy.<\/li>\r\n \t
                          • When levels get low<\/strong>, especially during hunger, fasting, or starvation:\r\n
                              \r\n \t
                            • Alpha cells<\/strong> in the pancreas are stimulated to\u00a0secrete glucagon<\/strong>.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n

                              Role of Glucagon<\/strong><\/h1>\r\n
                                \r\n \t
                              • Works in\u00a0opposition<\/strong>\u00a0to insulin.<\/li>\r\n \t
                              • When blood glucose levels are low,<\/strong> glucagon is secreted by pancreatic alpha cells.<\/li>\r\n \t
                              • \u00a0Glucagon:\r\n
                                  \r\n \t
                                1. Signals the\u00a0liver<\/strong>\u00a0to produce and release\u00a0glucose<\/strong>.<\/li>\r\n \t
                                2. Triggers\u00a0gluconeogenesis and glycogenolysis<\/strong>:\r\n
                                    \r\n \t
                                  • \r\n
                                      \r\n \t
                                    • Neo-<\/strong>\u00a0= new,\u00a0gluco-<\/strong>\u00a0= glucose,\u00a0-genesis<\/strong>\u00a0= creation.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
                                    • Liver gluconeogenesis<\/strong> produces additional glucose from:\r\n
                                        \r\n \t
                                      1. Proteins<\/strong>\u00a0(via protein breakdown)<\/li>\r\n \t
                                      2. Fats\/triglycerides<\/strong>\u00a0(via lipolysis)<\/li>\r\n<\/ol>\r\n<\/li>\r\n \t
                                      3. Liver glycogenolysis<\/strong> breaks down glycogen <\/strong>to produce even more glucose.<\/strong>\r\n
                                          \r\n \t
                                        • Glycogen<\/strong>\u00a0stores (glycogenolysis)<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ol>\r\n<\/li>\r\n<\/ul>\r\nOutcome:<\/strong>\r\n
                                            \r\n \t
                                          • Glucose enters the bloodstream.<\/li>\r\n \t
                                          • Blood glucose levels\u00a0return to normal<\/strong>, ensuring cells continue to receive energy.<\/li>\r\n \t
                                          • Ensures\u00a0cell function<\/strong>\u00a0and\u00a0brain energy supply<\/strong>\u00a0during fasting.<\/li>\r\n \t
                                          • Normal Blood Glucose Level Range:\u00a0 70 - 110 mg\/dL<\/li>\r\n<\/ul>\r\n

                                            Summary<\/strong><\/h1>\r\n
                                              \r\n \t
                                            • Insulin\u00a0lowers<\/strong>\u00a0blood glucose after meals.<\/li>\r\n \t
                                            • Glucagon\u00a0raises<\/strong>\u00a0blood glucose during fasting or low-glucose states to maintain blood glucose levels within the normal range (70-110mg\/dL) and therefore maintain homeostasis.<\/li>\r\n \t
                                            • Both hormones act\u00a0oppositely<\/strong>\u00a0to maintain blood glucose within the healthy range.<\/li>\r\n \t
                                            • This\u00a0dynamic regulation<\/strong>\u00a0maintains blood glucose levels within a narrow, healthy range, vital for normal cellular function and energy homeostasis.<\/li>\r\n<\/ul>","rendered":"

                                              Blood Glucose Homeostasis<\/strong><\/p>\n

                                              Pancreatic Hormones – Glucagon and Insulin:<\/strong><\/h1>\n
                                                \n
                                              • The pancreas produces\u00a0two main hormones<\/strong>\u00a0involved in regulating blood glucose:\n
                                                  \n
                                                • Insulin<\/strong>\u00a0(produced by beta cells)<\/li>\n
                                                • Glucagon<\/strong>\u00a0(produced by alpha cells)<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n

                                                  Post-Meal: Regulation of Blood Glucose<\/strong><\/h1>\n

                                                  Step 1: Post-Meal Rise in Blood Glucose Levels<\/strong><\/p>\n

                                                    \n
                                                  • After eating, glucose enters the bloodstream, causing\u00a0blood glucose levels to rise<\/strong>.<\/li>\n
                                                  • Elevated blood glucose\u00a0stimulates beta cells<\/strong>\u00a0in the pancreas to release insulin<\/strong>.<\/li>\n<\/ul>\n

                                                    Role of Insulin<\/strong><\/h1>\n
                                                      \n
                                                    1. Insulin facilitates the transport of glucose<\/strong>\u00a0into the body’s cells, by stimulating the insertion of GLUT4 glucose transporters<\/strong> into the cell membranes of the body\u2019s cells.\n
                                                        \n
                                                      • \n
                                                          \n
                                                        • Insulin<\/strong> binds to insulin receptors<\/strong> on cell membranes.<\/li>\n
                                                        • Triggers GLUT 4<\/strong> vesicles<\/strong> to move to the membrane and insert.<\/li>\n<\/ul>\n<\/li>\n
                                                        • Cells are then able to uptake glucose from the bloodstream.\n
                                                            \n
                                                          • Glucose is water-soluble and need a membrane transporter to enter cells.<\/li>\n
                                                          • Prevents\u00a0cell starvation<\/strong> in glucose, the vital energy source (required for ATP production)..<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n
                                                          • Insulin facilitates ATP production:\n
                                                              \n
                                                            • Glucose<\/strong> is used by cells to generate ATP<\/strong> through:\n
                                                                \n
                                                              • Anaerobic cellular respiration<\/strong> (Glycolysis) in which Glucose \u2192 Pyruvate + 2 ATP<\/strong><\/li>\n
                                                              • Aerobic cellular respiration<\/strong> (Krebs\/Citric Acid\/Tricarboxylic Acid Cycle) and Electron Transport Chain in which Glucose is broken down to produce 30-32 ATP<\/strong><\/li>\n<\/ul>\n<\/li>\n
                                                              • Without insulin, glucose remains in blood, leading to\u00a0hyperglycemia<\/strong>, and cells would be deprived of energy, impairing ATP production.<\/li>\n<\/ul>\n<\/li>\n
                                                              • Insulin stimulates glycogenesis<\/strong> (glycogen synthesis) in liver<\/strong> and skeletal muscle<\/strong>.\n
                                                                  \n
                                                                • Glycogen is a fuel storage molecule that can be broken down into glucose.<\/li>\n<\/ul>\n<\/li>\n
                                                                • Insulin also promotes the uptake<\/strong> of amino acids<\/strong> and lipids<\/strong> by cells which supports\n
                                                                    \n
                                                                  • Supports protein synthesis,<\/strong> cellular growth<\/strong> and maintenance<\/strong> and healing<\/strong>\n
                                                                      \n
                                                                    • Insulin influences gene expression and growth regulation!<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n
                                                                    • Insulin additionally promotes triglyceride<\/strong> synthesis in adipocytes<\/strong> (for storage of lipids as triglycerides)<\/li>\n<\/ol>\n

                                                                      Outcome:<\/strong>
                                                                      \n\u2022 Blood glucose levels decrease back to normal, maintaining homeostasis.<\/strong><\/p>\n

                                                                      Between Meals: Low Blood Glucose<\/strong><\/h1>\n
                                                                        \n
                                                                      • Blood glucose levels\u00a0drop<\/strong>\u00a0as cells use glucose for energy.<\/li>\n
                                                                      • When levels get low<\/strong>, especially during hunger, fasting, or starvation:\n
                                                                          \n
                                                                        • Alpha cells<\/strong> in the pancreas are stimulated to\u00a0secrete glucagon<\/strong>.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n

                                                                          Role of Glucagon<\/strong><\/h1>\n
                                                                            \n
                                                                          • Works in\u00a0opposition<\/strong>\u00a0to insulin.<\/li>\n
                                                                          • When blood glucose levels are low,<\/strong> glucagon is secreted by pancreatic alpha cells.<\/li>\n
                                                                          • \u00a0Glucagon:\n
                                                                              \n
                                                                            1. Signals the\u00a0liver<\/strong>\u00a0to produce and release\u00a0glucose<\/strong>.<\/li>\n
                                                                            2. Triggers\u00a0gluconeogenesis and glycogenolysis<\/strong>:\n
                                                                                \n
                                                                              • \n
                                                                                  \n
                                                                                • Neo-<\/strong>\u00a0= new,\u00a0gluco-<\/strong>\u00a0= glucose,\u00a0-genesis<\/strong>\u00a0= creation.<\/li>\n<\/ul>\n<\/li>\n
                                                                                • Liver gluconeogenesis<\/strong> produces additional glucose from:\n
                                                                                    \n
                                                                                  1. Proteins<\/strong>\u00a0(via protein breakdown)<\/li>\n
                                                                                  2. Fats\/triglycerides<\/strong>\u00a0(via lipolysis)<\/li>\n<\/ol>\n<\/li>\n
                                                                                  3. Liver glycogenolysis<\/strong> breaks down glycogen <\/strong>to produce even more glucose.<\/strong>\n
                                                                                      \n
                                                                                    • Glycogen<\/strong>\u00a0stores (glycogenolysis)<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n<\/li>\n<\/ul>\n

                                                                                      Outcome:<\/strong><\/p>\n

                                                                                        \n
                                                                                      • Glucose enters the bloodstream.<\/li>\n
                                                                                      • Blood glucose levels\u00a0return to normal<\/strong>, ensuring cells continue to receive energy.<\/li>\n
                                                                                      • Ensures\u00a0cell function<\/strong>\u00a0and\u00a0brain energy supply<\/strong>\u00a0during fasting.<\/li>\n
                                                                                      • Normal Blood Glucose Level Range:\u00a0 70 – 110 mg\/dL<\/li>\n<\/ul>\n

                                                                                        Summary<\/strong><\/h1>\n
                                                                                          \n
                                                                                        • Insulin\u00a0lowers<\/strong>\u00a0blood glucose after meals.<\/li>\n
                                                                                        • Glucagon\u00a0raises<\/strong>\u00a0blood glucose during fasting or low-glucose states to maintain blood glucose levels within the normal range (70-110mg\/dL) and therefore maintain homeostasis.<\/li>\n
                                                                                        • Both hormones act\u00a0oppositely<\/strong>\u00a0to maintain blood glucose within the healthy range.<\/li>\n
                                                                                        • This\u00a0dynamic regulation<\/strong>\u00a0maintains blood glucose levels within a narrow, healthy range, vital for normal cellular function and energy homeostasis.<\/li>\n<\/ul>\n","protected":false},"author":1370,"menu_order":12,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":["zoe-soon"],"pb_section_license":"cc-by-nc-sa"},"chapter-type":[],"contributor":[60],"license":[57],"class_list":["post-5103","chapter","type-chapter","status-web-only","hentry","contributor-zoe-soon","license-cc-by-nc-sa"],"part":63,"_links":{"self":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapters\/5103","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/wp\/v2\/users\/1370"}],"version-history":[{"count":16,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapters\/5103\/revisions"}],"predecessor-version":[{"id":5250,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapters\/5103\/revisions\/5250"}],"part":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/parts\/63"}],"metadata":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapters\/5103\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/wp\/v2\/media?parent=5103"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapter-type?post=5103"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/wp\/v2\/contributor?post=5103"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/wp\/v2\/license?post=5103"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}