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23 Cards in this Set
- Front
- Back
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What is normal blood glucose?
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4.5-7.0 mM
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How is blood glucose maintained?
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The actions of hypoglygaemic hormone INSULIN and the hyperglycaemic hormone GLUCAGON.
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What are the two main glucose homeostatic hormones and how do they act?
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- Insulin promotes glucose uptake into cells, storage and usage to help lower blood glucose.
- Glucagon promotes glycogenolysis, gluconeogenesis and lipolysis to help raise blood glucose |
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What are the 4 main cells comprising the endocrine pancreas and what do they secrete?
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1. Beta cells secrete insulin
2. Alpha cells secrete glucagon 3. Delta cells secrete somatostatin 4. PP cells secrete polypeptide |
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What proportion of the blood flow does the endocrine pancreas receive?
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Blood supply is from afferent arterioles of the pancreatic duodenal arteries.
Although the endocrine pancreas takes up 2-3% of its mass, it recieves 20-30% of its blood flow |
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What is the autonomic nervous stimulation of the pancreas?
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Sympathetic - middle and greater splanchnic nerves
Parasympathetic - Vagas nerve |
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Describe briefly the composition of the insulin hormone
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- Small molecular weight protein
- Alpha chain and beta chain - Chains held together by disulfide bridges |
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What are the three main steps in the production of insulin?
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1. Pre-pro-insulin (mRNA in endoplasmic reticulum)
2. Pro-insulin (cleaved in trans golgi) 3. Insulin (C chain/peptide cleaved) |
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What are the clinical manifestations of wrong glucose level?
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Hyper (higher than 7mM)
Early - polyuria, weight loss, polydipsia Late - ketoacidosis, hyperventilation, stupor, coma Hypo (below 4mM) Early - palpatations, tachycardia, weakness, hunger, nausea Late - confusion, hypothermia, seizures, coma |
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What is a potent stimulator of glucagon release?
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L-arganine (high glucagon after large protein meal)
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How may glucagon be used clinically?
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Glucagon may be administered to counteract hypoglycaemic episodes and acute cardiac failure as glucagon increases the rate of cardiac contractions
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What does somatostatin do?
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Inhibits the release of insulin, glucagon and pancreatic polypeptide. It impedes nutrient absorption, thereby preventing an increase in blood glucose untill the insulin-glucagon system has taken full effect
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What stimulates insulin secretion?
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- increased glucose and amino acids
- increases acetylcholine - increased CCK - increased e-cadherin and connexin-36 - decreased neuropeptide Y - decreased somatostatin - decreased ghrelin |
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How does glucose enter the beta cell?
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Through GLUT2 transpoter on the cell membrane
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How does glucose stimulate insulin secretion?
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- Enters via GLUT2
- Glucokinase converts to glucose-6-kinase - Enters glycolysis - Produced pyruvate and ATP - Increased ATP & ADP inhibits K channel - Close of channel causes depolarisation - Voltage gated calcium channels open - Calcium influx - Ca causes release of Ca from ER - Ca leads to exocytosis of insulin granules |
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Name and describe the two main incretins that also stimulate insulin secretion
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GIP (gastric inhibitory peptide)
released from K cells in duodenum and jejunum GLP-1 (glucagon-like-peptide) released by L-cells in ileum and colon |
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What drugs can be used for type-1 diabetes?
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Type-2 (non insulin dependent) diabetes can be treated with sulfonylureas which cause depolarisation of the beta cells by binding to SUR subunit next to the K channel, ultimately causing exocytosis of insulin vesicles
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Describe the different medications fro diabetes.
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Type 1 - insulin has to be injected
Type 2 - sulfonylureas can be taken orally |
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Why cant type 1 diabetes be treated orally?
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The beta cells in type 1 diabetes are destroyed and these patients must be treated with insulin replacement. There are no beta cells for the sulfonylurea drug to act upon and stimulate
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How does insulin stimulate the uptake of glucose in muscles and adipose tissue?
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Once insulin binds to the alpha subunits of the insulin receptor and beta subunits transmits signal to the cytoplasm an intracellular signalling cascade is set off. This results in the mobilization of GLUT4 vesicles to the membrane and subsequent integration into the plasma membrane
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What are the three main diabetic complications?
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- Diabetic retinopathy
- Diabetic nephropathy - Diabetic neuropathy |
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How does diabetes cause vascular disturbances?
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- Micro basement membrane thickens, reversible if BG controlled
- Macro atherosclerosis occurs mainly at coronary, cerebral and peripheral arteries |
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What are the different type of diabetic retinopathy?
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Background - mildest form, blot haemorrhages/cotton wool spots on examination, areas of retinal ischaemia
Proliferative - 5-10% progress, caused by retinal neuvascular proliferation, new vessels prone to bleeding |
