Hormonal Regulation of Blood Glucose Levels
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Created by:
fraittrain on January 4, 2011
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Description:
Brief Overview of Hormonal Regulation of Blood Glucose Levels
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9 terms
Terms | Definitions |
|---|---|
 What is the predominant tissue involved in RESPONDING to signals that indicate reduced or elevated blood glucose levels? | Liver |
| What cells secrete insulin? What is insulin's primary role? | beta cells of the islets of Langerhans; it is the ONLY hormone that lowers blood glucose. Elevated blood glucose triggers release of insulin from pancreatic beta islet cells. |
| How does insulin alter the metabolic pathways of glucose metabolism? | enhances the synthesis of glycogen, lipid & protein while inhibiting the breakdown of glycogen |
| In what form is insulin synthesized? | It is synthesized as a precursor called preproinsulin, a single chain polypeptide. Proinsulin is a further edited rendition (N-terminal signal sequence removed) made up of B chain, C chain & A chain. The C peptide (C chain) is cleaved out to form insulin. |
| Where is preproinsulin stored after synthesis? | In vesicles in the beta islet cells of the pancreas |
| Describe how insulin ends up being released from the beta islet of Langerhans cells? Describe the role of Calcium. | Excess blood glucose. Glucose flows into the beta cells via GLUT 2 & 4, glycolysis-TCA-ETC takes place, dramatically increasing intracellular concentration of ATP. Increase in intracellular ATP blocks ATP dependent K+ channels (KATP), leading to depolarization of cell, leading to opening of voltage gated calcium channels permitting inflow of Ca2+. Ca2+ can attach onto preproinsulin vesicles causing them to fuse w/ the PM. Ca2+ can also bind to CREB (Calcium Responsive Element Binding Protein) on DNA to upregulate transcription & translation of insulin gene. |
| What is the role of GLP-1 (Glucagon-like protein 1) in insulin secretion? When is it released and what is its effect on insulin secretion? | It is aka incretin. It upregulates insulin secretion. Mucosal cells produce it during periods of carbohydrate absorption (blood is about to be flooded w/ glucose). It is a secretagogue - a substance that causes the release of something else & is an example of an insulinotropic peptide - "insulin-loving" peptide. |
| What does GLP-1 inhibit? | inhibits glucagon secretion from the α-cells of the pancreas, inhibits gastric emptying, lowers food intake [we have enough nrg!], stimulates neogenesis and proliferation of β-cells and inhibits apoptosis of β-cells [insulin is needed]. |
| What is the role of insulin in its own secretion? | Insulin activates the secretion of its own gene as well as the beta islet cell glucokinase gene - beta cell glucokinase increases the rate of glycolysis. This means higher ATP levels, KATP shutdown etc etc... more insulin secretion & production! |
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