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Physiology > Pancreas > Flashcards

Pancreas Flashcards

1
Q

What are the major cells in the Islets of Langerhans?

A 
Alpha
Beta
Delta
PP
Epsilon
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2
Q

What is the function of alpha cells?

A

Make glucagon

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3
Q

What is the function of beta cells?

A

Make insulin

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4
Q

What is the function of delta cells?

A

Make somatostatin (SS14)

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5
Q

What is the function of PP cells?

A

Secrete pancreatic polypeptide

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6
Q

What is the function of epsilon cells?

A

Make ghrelin

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7
Q

What is the major function of insulin?

A

Energy storage (anabolic hormone)

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8
Q

What is the major function of glucagon?

A

Energy mobilization (catabolic hormone)

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9
Q

Describe the arrangement of alpha and beta cells.

A

Beta cells clustered in “core”; other cells in “mantle.”

Alpha cells surround beta cells in a sandwich formation and the line the outer capillaries.

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10
Q

How does blood flow in the Islets of Langerhans?

A

Blood feeds the center of the Islet and then

flows outward

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11
Q

Describe the processing of insulin.

A

Insulin is released with C-peptide and the C chain is cleaved off which is necessary for insulin to bind to its receptor

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12
Q

What is the function of C-peptide?

A

C peptide has a long half life in the blood and is used to measure pancreatic function

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13
Q

How does glucose outside of the beta cell stimulate the initiation of insulin release?

A

Transported into cell by GLUT-2, which has LOW affinity for glucose. Only when glucose is high will it transport.

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14
Q

What happens to glucose once it is transported into the beta cell?

A

Glucose will be turned into G6P only when the glucose levels are high as glucokinase has a low affinity for glucose.

G6P will be metabolized and it will generate ATP.

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15
Q

What happens with increased ATP levels in the beta cell?

A

Increased ATP will cause the cell’s K+ channels to close and as a result, K+ will accumulate within the cell.

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16
Q

What is the function of sulfonylurea drugs?

A

They will also close the K+ channels in the beta cell, bypassing the glucose steps

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17
Q

What happens with increased K+ within the beta cell?

A

It will cause the cell to depolarize and Ca2+ channels to open.

18
Q

What happens to the beta cell with the opening of the Ca2+ channels?

A

The Ca2+ influx will will cause the exocytosis of insulin vesicles

19
Q

How do FFAs and AAs affect insulin release?

A

They will increase it as both can generate ATP within the beta cell as well

20
Q

What is the biphasic insulin response following a meal?

A

1 - there is an initial insulin spike signaling the release of insulin that has already been docked at the membrane

2 - the rising slope after the drop signals newly synthesized insulin being released

21
Q

What is the insulin receptor and how does it work?

A

It is a tyrosine kinase receptor and insulin binds receptor at alpha subunit and the beta subunit is autophosphorylated

22
Q

What is the action of insulin in the muscle cell?

A

It allows for muscles to uptake glucose via GLUT4, otherwise, muscles cannot intake glucose.

23
Q

What is the pathway for insulin action of the muscle cell?

A
  • Autophosphorylation of receptor recruits IRSs (insulin receptor substrates).
  • IRSs activate intracellular signaling cascades

RESULT: GLUT-4 inserted in membrane – glucose can enter cell

24
Q

Which of the glucose transporters is glucose independent?

A

GLUT-1, 2, 3 are all insulin independent

25
Q

What glucose transporter is glucose dependent?

A

GLUT-4 in muscle

26
Q

What is the effect of insulin on the liver?

A

Promotes glycogen and TAG production Reduces glucose production/output

27
Q

What is the effect of insulin on muscle?

A

Promotes glycogen and TG production and protein synthesis

28
Q

What is the effect of insulin on fat?

A

Promotes TAG production, release of FFAs from chylomicrons, glycolysis

29
Q

How is glucagon processed in the pancreatic alpha cell?

A

GRPP is cleaved from GLUC and is inactive

GLP-1 and 2 (Incretins) are not cleaved an inactive

GLUC is cleaved free and is active

30
Q

How is glucagon processed in the intestinal L cell?

A

GRPP-GLUC is not cleaved and remains inactive as glicentin

The incretins GLP-1 and 2 are cleaved in the intestine and active.

31
Q

What is the function of incretins?

A

They increase the amount of insulin released from the pancreas

32
Q

When is glucagon released?

A

Major counterregulatory hormone to insulin – most things that stimulate insulin will inhibit glucagon.

Released in response to low blood glucose levels.

33
Q

What effect do AAs have on glucagon release?

A

AAs stimulate release (protein meals)

34
Q

What effect do catecholamines have on glucagon release?

A

Catecholamines stimulate release (exercise)

35
Q

What is the effect of insulin on ketogenesis?

A

Insulin will inhibit ketogenesis

36
Q

What is the function of somatostatin (SS14)?

A

Suppresses insulin release - used in clinic for management of insulin-producing tumors

37
Q

What is the regulation of SS14?

A

Produced by delta cells in pancreatic islets
Stimulated by high fat, high carb meals.
Inhibited by insulin

38
Q

What is the function of amylin?

A

Released with insulin from vesicles in beta cells

Synergistic with insulin in regulation of blood glucose

39
Q

What is the function of ghrelin?

A

Stimulates food intake at level of hypothalamus
Stimulates GH release
Inverse correlation between circulating ghrelin and obesity

40
Q

What are the main counter regulatory hormones to insulin?

A

Glucagon
Growth Hormone
Cortisol
Catecholamines

Physiology (81 decks)

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