Endo - Anatomy & Physio (Endocrine pancreas, Insulin, & Glucagon)

Question 1

From where do the Islets of Langerhans arise? Of what cells do they consist?

Answer 1

Islets arise from pancreatic buds; Alpha, Beta, and delta endocrine cells

Question 2

Again, what are the cells in the Islets of Langherhans? What is the product of each, and where is each found in the Islet?

Answer 2

(1) Alpha = glucagon (peripheral) (2) Beta = insulin (central) (3) Delta = somatostatin (interspersed); Think: “INsulin (Beta cells) = INside”

Question 3

Draw a pancreatic Islet, labelling the following: (1) Alpha Cell (2) Beta cell (3) Delta cell (4) Capillaries.

Answer 3

See First Aid 2014 p. 307 or 2013 p. 287

Question 4

From where is Insulin released?

Answer 4

Released from (Beta) cells of pancreas

Question 5

What is a major regulator of insulin release? What is its mechanism of regulation?

Answer 5

Glucose; ATP generated by glucose metabolism closes K+ channels and depolarizes Beta cell membrane –> opens voltage-gated Ca2+ channels –> Ca2+ influx stimulates insulin secretion

Question 6

What effect does Insulin have on glucose?

Answer 6

Insulin moves glucose into cells; Think: “INsulin moves glucose INto cells”

Question 7

Do insulin and/or glucose cross the placenta?

Answer 7

Insulin does NOT cross the placenta, unlike glucose

Question 8

Which parts of the body have insulin-independent glucose reuptake?

Answer 8

Brain, RBCs, Intestine, Cornea, Kidney, Liver; Think: “BRICK L(P) [P for Pancreatic Beta cells]”

Question 9

Draw proinsulin, labeling the following: (1) Alpha chain (2) C peptide (3) Beta chain (4) Disulfide bonds.

Answer 9

See First Aid 2014 p. 308 to right or 2013 p. 288 to left

Question 10

Is insulin anabolic or catabolic?

Answer 10

Anabolic

Question 11

What are the 7 anabolic effects of insulin?

Answer 11

(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

Question 12

What effect does insulin have on glucose transport in skeletal muscle and adipose?

Answer 12

Increase

Question 13

What effect does insulin have on glycogen synthesis/storage and triglyceride synthesis/storage?

Answer 13

Increase both

Question 14

What effect does insulin have on sodium retention by kidneys?

Answer 14

Increase

Question 15

What effect does insulin have on protein synthesis? To which part(s) of the body is this most relevant?

Answer 15

Increase; Muscles

Question 16

What effect does insulin have on cellular uptake of K+ and amino acids?

Answer 16

Increase

Question 17

What effect does insulin have on glucagon release?

Answer 17

Decrease

Question 18

What factors increase insulin?

Answer 18

(1) Hyperglycemia (2) Beta2-agonists (3) GH (causes insulin resistance –> increased insulin release)

Question 19

What role does GH play in insulin regulation?

Answer 19

GH increases insulin resistance, leading indirectly to increased insulin secretion

Question 20

What factors decrease insulin?

Answer 20

(1) Hypoglycemia (2) Somatostatin (3) Alpha2-agonists

Question 21

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.

Answer 21

See First Aid 2014 Pg. 308 near bottom right or 2013 Pg. 288 Near bottom left

Question 22

What are the steps involved in insulin secretion by pancreatic Beta cells? Where does insulin go upon its release?

Answer 22

(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)

Question 23

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.

Answer 23

See First Aid 2014 Pg. 308 near bottom left or 2013 Pg. 288 near bottom right

Question 24

What are the steps involved in glucose uptake by insulin-dependent cells?

Answer 24

(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

Question 25

Again, which tissues depend on insulin for glucose reuptake? Which transporter do they use?

Answer 25

Resting skeletal muscle and adipose tissue depend on insulin for increased glucose reuptake (via GLUT-4)

Question 26

On what does the brain depend for metabolism under normal circumstances? What does it use in starvation?

Answer 26

Glucose; Ketone bodies

Question 27

What do RBCs always depend on for metabolism, and why?

Answer 27

Glucose; They have no mitochondria for aerobic metabolism

Question 28

What is the source of Glucagon?

Answer 28

Made by Alpha cells of the pancreas

Question 29

Is Glucagon anabolic or catabolic?

Answer 29

Catabolic

Question 30

What are the catabolic effects of Glucagon?

Answer 30

(1) Glycogenolysis, Gluconeogenesis (2) Lipolysis and ketone production

Question 31

What stimulates secretion of Glucagon?

Answer 31

Hypoglycemia

Question 32

What inhibits secretion of Glucagon?

Answer 32

(1) Insulin (2) Hyperglycemia (3) Somatostatin

Question 33

Describe the process of synthesizing insulin by providing its 5 steps.

Answer 33

Preproinsulin (synthesized in RER) --> cleavage of "presignal" --> proinsulin (stored in secretory granules) --> cleavage of proinsulin --> exocytosis of insulin and C-peptide equally

Question 34

How is insulinoma distinguished from exogenous insulin?

Answer 34

Insulin and C-peptide are increased in insulinoma, whereas exogenous insulin lacks C-peptide

Question 35

What is the mechanism of insulin? More specifically, what does it bind, and what does this binding induce?

Answer 35

Binds insulin receptors (tyrosin kinase activity), inducing glucose uptake (carrier-mediated transport) in insulin-dependent tissue and gene transcription

Question 36

Is GLUT-4 an insulin dependent or independent glucose transporter? Where is it found (2 places)?

Answer 36

Insulin-dependent glucose transporters: GLUT-4: (1) adipose tissue, (2) skeletal muscle

Question 37

Is GLUT-1 an insulin dependent or independent glucose transporter? Where is it found (3 places)?

Answer 37

Insulin-independent transporters: GLUT-1: (1) RBCs (2) Brain (3) Cornea

Question 38

Is GLUT-5 an insulin dependent or independent glucose transporter? With what sugar is it associated? Where is it found (2 places)?

Answer 38

Insulin-independent transporters: GLUT-5 (fructose): (1) Spermatocytes (2) GI tract

Question 39

Is GLUT-2 an insulin dependent or independent glucose transporter? What is its directionality? Where is it found (4 places)?

Answer 39

Insulin-independent transporters: GLUT-2 (bidirectional): (1) Beta islet cells (2) liver (3) kidney (4) small intestine

Question 40

What are the insulin-independent glucose transporters?

Answer 40

GLUT-1, GLUT-5, GLUT-2

Question 41

Which glucose transporter is associated with fructose?

Answer 41

Insulin-dependent transporters: GLUT-5 (fructose): (1) Spermatocytes (2) GI tract

Question 42

Which glucose transporter is bidirectional?

Answer 42

Insulin-dependent transporters: GLUT-2 (bidirectional): (1) Beta islet cells (2) liver (3) kidney (4) small intestine

Question 43

What is the major regulator of insulin release?

Answer 43

Glucose is major regulator of insulin release

Question 44

What are the steps leading to insulin secretion from pancreatic Beta cells?

Answer 44

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