Pancreatic Hormones

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  • Created by: Becca
  • Created on: 26-12-13 13:00
What & where are the isolated hormone secreting cells of the GI tract? What do they do?
Peptide & Amine hormones (e.g. gastring, serotonin) secreted by gut wall, regulate activity of GI tract, pancreas etc, along with ANS. Open type secrete onto surface. Closed type secrete deep to surface (receptive to changes in tissue environment)
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What is the function of the pancreas? Where are endocrine cells found?
Both exocrine & endocrine functions. Endocrine cells found in scattered groups called the islets of Langerhans, only comprise 1-2% of the volume but receive 20% of the blood supply
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What is the blood supply & innervation to the pancreas?
Splenic, superior & inferior pancreaticoduodenal arteries. Veins tributaries of splenic & superior mesenteric portal veins. Innervation: sympathetic (abdominopelvic splanchnic) & parasympathetic (vagal)
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What is the histology of the pancreas?
Majority exocrine with endocrine islet spots scattered (no distribution or size pattern)
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What are the 3 hormones of the pancreas? Which cells secrete them?
Insulin - beta cells. Glucagon - alpha cells. Somatostatin - delta cells
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What is the histology & prevalence of the pancreatic cells?
Alpha cells: 18%, homogeneous dense spheres. Beta cells: 75%, homogeneous crystals, loose membrane. Delta cells: 3%, heterogeneous large spheres
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What is the biochemistry of insulin?
Synthesised in B-cells, consists of 2 peptides (A/B chains) connected by 2 disulphide bridges & intra-chain (A, disulphide bond). Hydrophilic (soluble), transported as free molecule, vulnerable to metabolic deactivation -> short half life
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How is insulin synthesised?
Gene transcription/translation rER -> preproinsulin, signal sequence cleaved, pro-insulin (insulin + C-peptide, biologically inactive) buds into vesicles -> Golgi, C-peptide cleaved -> Insulin
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How is the C-peptide cleaved to turn pro-insulin into insulin?
Proconvertase 1 (PC1) cleaves at amino acids 32+33, PC2 cleaves at amino acids 65+66 -> Carboxypeptidase H removes 31+32 of B chain & 64+65 of C peptide
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What happens to insulin once the C-peptide has been removed?
Condensation of insulin with Zn2+ (2 Zn:6 insulin), crystalloid core in secretory granules, stored until required. Insulin released via exocytosis using Ca2+ & ATP
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What stimulates insulin release?
Blood glucose: rise in ATP:ADP, ATP-sensitive K channels close, depolarisation, voltage-gated Ca channels open, insulin release. Neural: sympathetic (B-adrenoceptors increase realease, alpha decrease) & parasym (muscarinic receptors increase release)
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What are the actions of insulin?
Promote growth & development/cellular uptake of K (via Na/K ATPase pump)/glucose uptake & utilisation/fuel storage (anabolic, promotes storage of fat/glycogen/protein). LOWERS BLOOD GLUCOSE
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What synthesises glucagon? What stimulates & inhibits its release?
Peptide hormone synthesised as pro-glucagon in alpha cells. Release stimulated by low blopd glucose, para & sympathetic NS & amino acids. Inhibited by high blood glucose, insulin & somatostatin
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What are the actions of glucagon?
ELEVATES BLOOD GLUCOSE, stimulate hepatic glycogenolysis, hepatic gluconeogenesis & lipolysis
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What is effect of increased blood glucose on glucagon & insulin?
Inhibits alpha cells -> decrease glucagon & stimulates beta cells -> increase insulin. Lowers blood glucose back to normal levels
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What is the effect of decreased blood glucose on glucagon & insulin?
Stimulates alpha cells -> increase glucagon & inhibits beta cells -> decrease insulin. Raises blood glucose back to normal
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Where is somatostatin synthesised? What is its role?
Peptide hormone synthesised as pro-hormone in delta cells, also in CNS (hypothalamus) & GIT. Inhibits both glucagon & insulin secretion by a paracrine mechanism
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Card 2

Front

What is the function of the pancreas? Where are endocrine cells found?

Back

Both exocrine & endocrine functions. Endocrine cells found in scattered groups called the islets of Langerhans, only comprise 1-2% of the volume but receive 20% of the blood supply

Card 3

Front

What is the blood supply & innervation to the pancreas?

Back

Preview of the front of card 3

Card 4

Front

What is the histology of the pancreas?

Back

Preview of the front of card 4

Card 5

Front

What are the 3 hormones of the pancreas? Which cells secrete them?

Back

Preview of the front of card 5
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