Endo - Anatomy & Physio (Endocrine pancreas, Insulin, & Glucagon) Flashcards
Pg. 307-309 in First Aid 2014 or Pg. 287-289 in First Aid 2013 Sections include: -Endocrine pancreas cell types -Insulin -[In FA 2013, Insulin-dependent organs] -Glucagon
From where do the Islets of Langerhans arise? Of what cells do they consist?
Islets arise from pancreatic buds; Alpha, Beta, and delta endocrine cells
Again, what are the cells in the Islets of Langherhans? What is the product of each, and where is each found in the Islet?
(1) Alpha = glucagon (peripheral) (2) Beta = insulin (central) (3) Delta = somatostatin (interspersed); Think: “INsulin (Beta cells) = INside”
Draw a pancreatic Islet, labelling the following: (1) Alpha Cell (2) Beta cell (3) Delta cell (4) Capillaries.
See First Aid 2014 p. 307 or 2013 p. 287
From where is Insulin released?
Released from (Beta) cells of pancreas
What is a major regulator of insulin release? What is its mechanism of regulation?
Glucose; ATP generated by glucose metabolism closes K+ channels and depolarizes Beta cell membrane –> opens voltage-gated Ca2+ channels –> Ca2+ influx stimulates insulin secretion
What effect does Insulin have on glucose?
Insulin moves glucose into cells; Think: “INsulin moves glucose INto cells”
Do insulin and/or glucose cross the placenta?
Insulin does NOT cross the placenta, unlike glucose
Which parts of the body have insulin-independent glucose reuptake?
Brain, RBCs, Intestine, Cornea, Kidney, Liver; Think: “BRICK L(P) [P for Pancreatic Beta cells]”
Draw proinsulin, labeling the following: (1) Alpha chain (2) C peptide (3) Beta chain (4) Disulfide bonds.
See First Aid 2014 p. 308 to right or 2013 p. 288 to left
Is insulin anabolic or catabolic?
Anabolic
What are the 7 anabolic effects of insulin?
(1) Increased glucose transport in skeletal muscle and adipose (2) Increased glycogen synthesis and storage (3) Increased triglyceride synthesis and storage (4) Increased Na+ retention (kidneys) (5) Increased protein synthesis (muscles) (6) Increased cellular reuptake of K+ and amino acids (7) Decreased glucagon release
What effect does insulin have on glucose transport in skeletal muscle and adipose?
Increase
What effect does insulin have on glycogen synthesis/storage and triglyceride synthesis/storage?
Increase both
What effect does insulin have on sodium retention by kidneys?
Increase
What effect does insulin have on protein synthesis? To which part(s) of the body is this most relevant?
Increase; Muscles
What effect does insulin have on cellular uptake of K+ and amino acids?
Increase
What effect does insulin have on glucagon release?
Decrease
What factors increase insulin?
(1) Hyperglycemia (2) Beta2-agonists (3) GH (causes insulin resistance –> increased insulin release)
What role does GH play in insulin regulation?
GH increases insulin resistance, leading indirectly to increased insulin secretion
What factors decrease insulin?
(1) Hypoglycemia (2) Somatostatin (3) Alpha2-agonists
Draw a pancreatic Beta cell depicting insulin secretion. Include the following steps: (1) GLUT-2 transport (2) Increase in ATP/ADP ration (3) ATP-sensitive K+ channels close (4) Depolarization (5) Increase in Intracellular Ca2+ (6) Exocytosis of insulin granules.
See First Aid 2014 Pg. 308 near bottom right or 2013 Pg. 288 Near bottom left
What are the steps involved in insulin secretion by pancreatic Beta cells? Where does insulin go upon its release?
(1) GLUT-2 transport (2) Increase in ATP/ADP ration (3) ATP-sensitive K+ channels close (4) Depolarization (5) Increase in Intracellular Ca2+ (6) Exocytosis of insulin granules; Enters blood vessel(s)
Draw a cell depicting insulin-dependent glucose uptake. Include the following labels: (1) Insulin (2) Tyrosine Phosphorylation (3) GLUT-4 (4) Glucose (5) Phosphoinositide-3 kinase pathway (6) RAS/MAP Kinase pathway (7) Vesicles containing GLUT-4 (8) Glucogen, lipid, and protein synthesis (9) Cell growth, DNA synthesis.
See First Aid 2014 Pg. 308 near bottom left or 2013 Pg. 288 near bottom right
What are the steps involved in glucose uptake by insulin-dependent cells?
(1) Insulin (binding its receptor) (2) Tyrosine phosphorylation (3a) Phosphoinositide-3 Kinase pathway –> Glycogen, lipid, protein synthesis AND Vesicles containing GLUT-4 (move transporter to membrane) (3b) RAS/MAP kinase pathway –> Cell growth, DNA synthesis
Again, which tissues depend on insulin for glucose reuptake? Which transporter do they use?
Resting skeletal muscle and adipose tissue depend on insulin for increased glucose reuptake (via GLUT-4)
On what does the brain depend for metabolism under normal circumstances? What does it use in starvation?
Glucose; Ketone bodies
What do RBCs always depend on for metabolism, and why?
Glucose; They have no mitochondria for aerobic metabolism
What is the source of Glucagon?
Made by Alpha cells of the pancreas
Is Glucagon anabolic or catabolic?
Catabolic
What are the catabolic effects of Glucagon?
(1) Glycogenolysis, Gluconeogenesis (2) Lipolysis and ketone production
What stimulates secretion of Glucagon?
Hypoglycemia
What inhibits secretion of Glucagon?
(1) Insulin (2) Hyperglycemia (3) Somatostatin
Describe the process of synthesizing insulin by providing its 5 steps.
Preproinsulin (synthesized in RER) –> cleavage of “presignal” –> proinsulin (stored in secretory granules) –> cleavage of proinsulin –> exocytosis of insulin and C-peptide equally
How is insulinoma distinguished from exogenous insulin?
Insulin and C-peptide are increased in insulinoma, whereas exogenous insulin lacks C-peptide
What is the mechanism of insulin? More specifically, what does it bind, and what does this binding induce?
Binds insulin receptors (tyrosin kinase activity), inducing glucose uptake (carrier-mediated transport) in insulin-dependent tissue and gene transcription
Is GLUT-4 an insulin dependent or independent glucose transporter? Where is it found (2 places)?
Insulin-dependent glucose transporters: GLUT-4: (1) adipose tissue, (2) skeletal muscle
Is GLUT-1 an insulin dependent or independent glucose transporter? Where is it found (3 places)?
Insulin-independent transporters: GLUT-1: (1) RBCs (2) Brain (3) Cornea
Is GLUT-5 an insulin dependent or independent glucose transporter? With what sugar is it associated? Where is it found (2 places)?
Insulin-independent transporters: GLUT-5 (fructose): (1) Spermatocytes (2) GI tract
Is GLUT-2 an insulin dependent or independent glucose transporter? What is its directionality? Where is it found (4 places)?
Insulin-independent transporters: GLUT-2 (bidirectional): (1) Beta islet cells (2) liver (3) kidney (4) small intestine
What are the insulin-independent glucose transporters?
GLUT-1, GLUT-5, GLUT-2
Which glucose transporter is associated with fructose?
Insulin-dependent transporters: GLUT-5 (fructose): (1) Spermatocytes (2) GI tract
Which glucose transporter is bidirectional?
Insulin-dependent transporters: GLUT-2 (bidirectional): (1) Beta islet cells (2) liver (3) kidney (4) small intestine
What is the major regulator of insulin release?
Glucose is major regulator of insulin release
What are the steps leading to insulin secretion from pancreatic Beta cells?
Glucose enters Beta cells –> increase in ATP generated from glucose metabolism –> closes K+ channels & depolarizes Beta cell membrane –> opens voltage-gated CA2+ channels, resulting in Ca2+ influx and stimulating insulin exocytosis
