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unit 6: physiology > Insulin and Glucagon > Flashcards

Insulin and Glucagon Flashcards

1
Q

What energy source lasts the longest: glucose, glycogen, protein, fat?

A

fat ! lasts 40 days

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2
Q

What interval is plasma glucose mantained at?

A

80-100 mg/dL

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3
Q

What do these cells of the islet of langerhan secrete:

  1. beta cells
  2. alpha cells
  3. delta cells
  4. F cells
A
  1. insulin
  2. glucagon
  3. somatostatin
  4. pancreatic polypeptide
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4
Q

What is the half life of glucagon?

A

3-4 minutes

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5
Q

Describe the processing of glucagon?

A

-secreted as 160 AA
-posttranslational processing:
glucagon -29
glicentin or enteroglucagon - 69
GLP, GLP1, GLP2

packaged and stored in membrane bound granules

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6
Q

What are four stimulators of glucagon secretion?

A
  1. hypoglycemia
  2. inc in arginine and alanine
  3. exercise
  4. stress
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7
Q

What are three inhibitors of glucagon secretion?

A
  1. somatostatin
  2. insulin
  3. hyperglycemia
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8
Q

What else is glucagon released in conjunction with, in response to stress?

A

catecholamines, growth hormone, cortisol

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9
Q

What is the primary target of glucagon?

A

liver

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10
Q

What three processes does glucagon induce?

A
  1. glycogenolysis
  2. gluconeogenesis
  3. lipolysis
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11
Q

What is proinsulin secreted with?

A

endopeptidase

and zinc

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12
Q

What is proinsulin cleaved into?

A

insulin and C-peptide

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13
Q

What does the level of C-peptide correlate to?

A

endogenous insulin production

in patients receiving exogenous insulin

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14
Q

What is the half life of insulin?

A

5-8 minutes

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15
Q

What is the pattern of insulin release after a meal? after an IV dose?

A

after a meal: fast release w/in 10 min and peaks about 30 min later

IV: first peak - stored insulin, falls in 10 min
if stim maintained - gradually inc during next hour

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16
Q

After glucose influxes through the cell through GLUT2 transporter, what are the next steps leading to insulin release?

A
  1. glucose metabolism - inc ATP
  2. ATP inhibits K+ channel
  3. Vm more positive –> depolarization
  4. activation of volt gated ca2+ channel
  5. ca2+ induced ca2+ release
  6. exocytosis of insulin granules
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17
Q

What other sugars besides glucose, and what AAs can also stimulate insulin release?

A

galactose and mannose

arginine and lysine (he also mentions leucine)

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18
Q

Is the effect of insulin inhibiting glucagon mutual?

A

NO glucagon stimulates insulin secretion

to prevent degradation in muscle

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19
Q

Why does oral glucose yield more insulin than IV glucose?

A

incretins provide advance notice of feeding and stimulate insulin secretion

CCK, GIP, GLP-1

20
Q

Does the PNS or SNS stimulate insulin secretion?

A

PNS

21
Q

What other hormones besides GIP, glucagon, and CCK enhance insulin secretion?

A

gastrin, secretin, VIP, epinephrine - B receptor

22
Q

What two hormones inhibit insulin secretion?

A

somatostatin and epinephrine - alpha receptor

23
Q

Which receptors of epinephrine are activated during exercise?

A

alpha and beta, but alpha predominates

24
Q

What is the net effect on insulin due to exercise?

A

it is suppressed - prevent hypoglycemia

25
Q

Does insulin or glucagon stimulate the synthesis of lipoprotein lipase to release fatty acids from chylomicrons and VLDL?

A

insulin

-increases the esterification of fats

26
Q

What happens during a glucose tolerance test for a patient with type 1 Diabetes?

A

plasma glucose rises to a higher level and remains there longer

27
Q

What can insulinemia result from?

A

insulin shots, insulinoma

28
Q

What can happen as a result of glucagonomas?

A

hyperglycemia

29
Q

What are orixigenic factors?

A

NTs that stimulate feeding

-neuropeptide Y

30
Q

What are anorexigenic factors

A

NTs that inhibit feeding

CRH, GLP-1, alpha MSH, CART

31
Q

What are satiety signals?

A

secreted in response to food ingestion

-CCK, GLP1, Glicentin, GLP2, NPY, ghrelin

32
Q

What message is CCK sending when it binds to CCK1 receptors on the vagus?

A

fat and protein is being processed and will soon be absorbed

33
Q

Where does the vagus send signals to?

A

NTS and then to the hypothalamus

34
Q

What is grhelin and what is it secreted by?

A

only hormone that stimulates food intake

-secreted by oxyntic glands in the stomach

35
Q

What is the target of ghrelin? what are the effects?

A

ARC

  1. inhibition of POMC/CART pathway
  2. enhance NPY. AgRP pathway
36
Q

What are adiposity signals?

A

leptin and insulin

hormones secreted in proportion to amount of fat in the body

37
Q

What is leptin derived from?

A

white adipocytes

38
Q

Are leptin and insulin able to cross the BBB?

A

yes

39
Q

What pathways does leptin and insulin inhibit/enhance?

A
  1. inhibits: AgRP/NPY
  2. enhances POMC–>alphaMSH

-decreases meal size

40
Q

What is the function of AgRP/NPY pathway?

A

stimulates food intake

41
Q

What is the function of the POMC pathway ?

A

inhibits the urge for food intake

42
Q

What does a leptin receptor mutation cause in humans and mice?

A

obesity

43
Q

What does a mutation in MC4R, the receptor for Alpha-MSH released from POMC cause??

A

obesity

44
Q

After weight loss what is the effect on:

  1. leptin
  2. insulin
  3. cck
  4. peptide YY
  5. Grhelin
  6. hunger
A
  1. leptin - reduced before diet, remains low
    2,3,4. insulin, CCK, Peptide YY
    -reduced at completion of diet, remains low
  2. grhelin - inc at completion of diet, remains high
  3. hunger - present and remains
45
Q

What does the study of the effect of hormones and diet determine?

A

long-term strategies to counteract hormonal response to diet programs may be needed to prevent obesity relapse

unit 6: physiology (13 decks)

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