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ER Week 2 > Endocrine Pancreas > Flashcards

Endocrine Pancreas Flashcards

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1
Q

What two organs is glycogen primarily stored in?

A

liver and muscles

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2
Q

How long can our glycogen stores last?

A

about 12 hours

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3
Q

What does our adipose tissue store? What’s the limit?

A

triglycerides

pretty much unlimited

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4
Q

What organs has virtually no energy stores?

A

the brain

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5
Q

What is the brain’s primary energy source? What will it settle for?

A

Glucose is preferred

but it will settle for ketone bodies

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6
Q

WHen you’re in the fasted state, what is the FIRST thing the body will do to increase blood glucose?

A

glycogen breakdown in the liver and muscle

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7
Q

How long does it take for reserves to be depleted with these two steps?

A

about 24 hours

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8
Q

What energy source will the will move toward as it goes into the starved state?

A

adipose triglycerides will be catabolized to glycerol and free fatty acids

the glycerol can be made into glucose and the free fatty acids can be used to make ketone bodies

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9
Q

What does insulin do to lypolysis? How

A

It inhibits lipolysis and promotes the storage of fatty acids as triglycerides

does so by:

  1. inhibiting intracellular lipases
  2. promoting accumulation of TGs in fat by facilitating entry of glucose into the adipocyte
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10
Q

What does insulin do to glucose oxidation?

A

promotes it

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11
Q

What does insulin do to glycogenolysis?

A

inhibits

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12
Q

What does insulin do to protein synthesis?

A

promotes it

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13
Q

What does glucagon do to glycogenogenesis?

A

inhibits it - promotes glycogenolysis

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14
Q

What does glucagon do to gluconeogenesis?

A

promotes it

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15
Q

What does glucagon do to ketogenesis?

A

promotes it

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16
Q

What is a normal blood glucose? How about a normal fasting blood glucose?

A

normal is about 70-120 mg/dL

fasting normal is less than 100 mg/dL

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17
Q

What are the 4 types of cells (per Rose-Hellekant) in an endocrin pancreas islet of langerhans?

A

alpha cells
beta cells
delta cells
epsilon cells

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18
Q

What do the alpha cells secrete?

A

glucagon

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19
Q

What do the beta cells secrete?

A

insulin and amylin

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20
Q

What do the delta cells secrete?

A

somatostatin

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21
Q

What do the epsilon cells secrete?

A

ghrelin

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22
Q

What effect will sympathetic nerves have on the beta cells?

A

they will inhibit insulin and amylin secretion during the fight or flight response

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23
Q

What effect will parasympathetic nerves via the vagus have on insulin secretion?

A

they increase insulin secretion during the cephalic phase

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24
Q

What effect will low plasma glucose have in terms of negative feedback in the islets?

A

will turn off the beta cells so you don’t secrete more insulin

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25
Q

What effect will high plasma glucose have in terms of negative feedback in the islets?

A

will turn off the alpha cells so you don’t secrete glucagon

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26
Q

What is insulin composed of?

A

two chains - an alpha and a beta - connected by two disulfide bridges

note - the sequence 22-26 in the beta chain is essential for biologic activity

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27
Q

What can be measured as an indicator of endogneous insulin production in diabetic patients?

A

C-peptide

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28
Q

What is the half life of insulin in the body? What metabolizes it?

A

less than 10 minutes

50% is metabolized in first pass metabolism in the liver and kidney - use proteolytic enzymes and glutathione-insulin transhydrogenase

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29
Q

What kind of receptor is the insulin receptor?

A

tyrosine kinase

30
Q

What molecule is co-secreted with insulin?

A

amylin

31
Q

What is the purpose of amylin?

A

it inhibits glucagon secretion at the level of the pancreatic alpha cell

also induces satiety (reduces food intake, delays gastric emptying, inhibits secretion of digestive enzymes, acid, and bile)

32
Q

Describe amylin’s recepto?

A

a calcitonin receptor that dimerizes with a receptor activity-modifying protein

33
Q

How is glucagon synthesized?

A

it’s synthesized as a proglucan in the pancreatc alpha cell

34
Q

Glucagon production will increase in response to what?

A
  1. hypoglycemia
  2. high amino acids (protects from hypoglycemia after an all-protein meal)
  3. sympathetic activity and vagal stimulation
35
Q

How can glucagon be stimulated by both sympathetic activity and vagal activity?

A

with sympathetics, it’s in response to the flight or fright response so that the body can use stored energy

with vagal stimulation, it’s to temper the insulin effects and make sure you don’t so super hypoglycemic

36
Q

Somatostatin release is triggered by what?

A

increased insulin

37
Q

WHat does somatostatin do in the pancreas?

A

inhibits secreton of insulin, glucagon and ghrelin

38
Q

What is the net effect of somatostatin in the GI tract?

A

reduce the rate of food absorption

39
Q

What hormone will inhibit somatostatin release?

A

ghrelin

40
Q

What will trigger ghrelin release?

A

hunger

41
Q

So if ghrelin is active when you’re hungry, what do you think it’s effect on glucagon is?

A

activates the alpha cells to secrete it

and inhibits beta cells

42
Q

What are incretins?

A

GI hormones that promote beta cell insulin release after eating

43
Q

What are the two main incretins?

A

glucagon-like peptide 1
(GLP-1)
and
Glucose dependent insulinotropic peptide (GIP)

44
Q

What are the net effects of the incretins in the GI tract?

A

slow the rate of absorption of nutrients into the blood stream by reducing gastric emptying and may directly reduce food intake

45
Q

What cells produce GLP-1?

A

L cells of the lower small itnestine and colon

46
Q

How is GLP-1 made?

A

it’s a product of alternative splicing from the proglucagon gene (vs in the pancreas, in which the spliced product is glucagon)

47
Q

GLP-1 is rapidly degraded by what enzyme?

A

dipeptidyl peptidase 4

48
Q

What cells make GIP?

A

K cells of the duodenum and jejunum

49
Q

What are the four phases of insulin secretion?

A
  1. cephalic phase
  2. oral phase
  3. GI phase
  4. Blood glucose phase
50
Q

What mediates the cephalic phase of insulin secreiton?

A

parasympathetic activity in response to sights and smells of foods

51
Q

What mediates the oral phase of insulin secretion?

A

parasympathetic information and carbohydrate sugar stimulation of sweet receptors

52
Q

What mediates the GI phase of insulin secreiton?

A

basically GIP and GLP-1

53
Q

True or false: the amount of insulin secreted is greater when the glucose is administered intravenously rather than orally.

A

false - it’s high when it’s oral because of the extra help provided by GIP and GLP-1 in the GI phase

54
Q

Describe the blood glucose phase.

A

that’s the easy one…

increased blood glucose activates the beta cells

decreased blood glucose activates the alpha cells

55
Q

What nonpancreatic hormones are involved in maintaining euglycemia by regulating the balance of glucagon and insulin?

A

catecholamines
cortisol
growth hormone

56
Q

What is the effect of catecholamines?

A

decrease insulin secretion
increase glucagon secretion

makes sense - you want to mobilized stored fuels for use if you fighting or fleeing

57
Q

What is the effect of cortisol on this balance?

A

no direct effect on insulin secreiton, but increased glucagon secretion (which then inhibits insulin anyways)

makes sense because one of cortisol’s main purposes is to help the body avoid hypoglycemia

58
Q

What is the effect of growth hormone on this system?

A

It increases both insulin and glucagon secretion

(I can’t make sense of this one)

but the net effect is towards the side of glucagon I think

59
Q

What transporter do the gut and kidney use for uptake of hexoses (including glucose) from food and urine?

A

sodium glucose co-transporters (SGLTs)

60
Q

What SGLT is mainly in the small intestine and which is almost exclusively in the kidney?

A

SGLT1 is mainly in the small itnestine

SGLT2 is almost exclusively in the kidney

61
Q

What type of transporters are used to maintain glucose homeostasis within the body?

A

various members of the GLUT protein family

62
Q

How many classes of GLUT transporters are there and which one do we care about?

A

3 - we mainly care about Class I because it contains GLUT1-4

63
Q

Which GLUT is located on most cells, including RBCs?

A

Glut1

it provides a low level basal uptake for glucose and is unique as the transporter for glucose across the blood brain barrier

64
Q

Which GLUT is on the mucosal surface of the small intestine and sperm?

A

GLUT5

65
Q

What is GLUT5 primarily concerned with?

A

it’s the primary fructose carrier in the intestine

66
Q

What GLUT is located on neurons, placenta and testes?

A

GLUT 3

67
Q

What Is the GLUT taht is insulin-sensitive?

A

GLUT 4

68
Q

What cells have GLUT 4?

A

skeletal muscle
cardiac muscle
fat

69
Q

What cells have GLUT 2?

A

liver, beta cells, kidney, hypothalamus, basolateral membrane of the small intestine

70
Q

What’s special about the GLUT 2 in the pancreas?

A

it is bidirectional, so it can act as the main part of the “glucose sensor” in the pancreas

71
Q

What GLUT transports glucose in the ER?

A

GLUT 7

72
Q

How does the pancreatic beta cell secrete insulin? What are the steps?

A
  1. a trigger (usually glucose) causes an increase in intracellular ATP
  2. The ATP closes a K channel
  3. Cell depolarizes
  4. opens a voltage gated Ca channel and Ca flow in the cell
  5. Ca makes the insulin-containing granules dock with the membrane and release insulin

ER Week 2 (10 decks)

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