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Endocrinology > Endocrine pancreas > Flashcards

Endocrine pancreas Flashcards

1
Q

Where does the pancreas lie?

A

Behind the stomach

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2
Q

What are the four regions of the pancreas?

A

Head
Neck
Body
Tail

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3
Q

Which three blood vessels does the pancreas lie in close proximity to?

A

Aorta, IVC

Hepatic portal vein

Superior mesenteric artery, vein

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4
Q

How does the pancreas develop embyrologically?

A

Outgrowth of foregut

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5
Q

What are the two groups of functions of the pancreas?

A

Exocrine functions

Endocrine functions

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6
Q

What are the exocrine functions of the pancreas?

A

Produce digestive enzymes

Produce alkali

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7
Q

Where does the pancreas pour its exocrine secretions into? Through what?

A

The duodenum

through the pancreatic duct

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8
Q

What are the endocrine functions of the pancreas?

A

Produces the following hormones

  • insulin
  • glucagon
  • somatostatin/GHIH
  • pancreatic poypeptide
  • ghrelin
  • gastrin
  • vasoactive intestinal peptide VIP
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9
Q

What type of hormone are the hormones secreted by the pancreas?

A

Polypeptide hormones

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10
Q

What is the name of the group of cells with endocrine function?

A

Islets of Langerhans

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11
Q

How do islets of Langerhans appear histologically?

A

Pale, isolated groups of cells

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12
Q

What type of endocrine cell produces insulin?

A

Beta cells

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13
Q

What type of endocrine cell produces glucagon?

A

Alpha cells

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14
Q

What type of endocrine cell produces somatostatin?

A

Delta cells

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15
Q

What type of endocrine cell produces pancreatic polypeptide?

A

Pancreatic polypeptide cells

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16
Q

What type of endocrine cell produces ghrelin?

A

e cells

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17
Q

What is the function of ghrelin?

A

Control of appetite

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18
Q

What type of endocrine cell produces gastrin?

A

G cells

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19
Q

Which type of endocrine cell forms the largest proportion of the islets of Langerhans?

A

Beta cells

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20
Q

The islets of Langerhans form what percentage of the pancreas?

A

1%

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21
Q

What is normal plasma glucose?

A

3.3 - 6 mmol/L

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22
Q

What is plasma glucose after a meal?

A

7-8 mmol/L

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23
Q

Why is it important that blood glucose is kept constant within a narrow range?

A

Brain preferably metabolises glucose
relies on blood glucose

Glucose affects osmolarity of blood
causes cells to shrink or swell
disrupts normal cellular function

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24
Q

What is meant by the renal threshold?

A

Concentration at which kidneys excrete substance into urine

Because can’t reabsorb any more

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25
Q

What is the renal threshold of glucose?

A

10mmol/L

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26
Q

What is glycosuria?

A

Glucose in the urine

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27
Q

When is the renal threshold of glucose increased?

A

Elderly

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28
Q

When is the renal threshold of glucose decreased?

A

Pregnancy

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29
Q

When is insulin released?

A

When plasma glucose is high

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30
Q

How do insulin and glucagon react to water?

A

Hydrophilic

Water-soluble

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31
Q

What is the advantage of insulin and glucagon being water-soluble?

A

Can dissolve in plasma

No special transport proteins required

32
Q

What is the half life of insulin and glucose? What is the advantage of this?

A

5 minutes

Have short-lived effects
Useful because plasma glucose conc. is always changing

33
Q

Where is insulin synthesised in the pancreatic beta cell?

A

ER

34
Q

What form of insulin is synthesised in the ER?

A

Preproinsulin

35
Q

How is preproinsulin modified in the ER?

A

Cleaved

to produce proinsulin

36
Q

Where is proinsulin transported to from the ER?

A

Golgi

37
Q

What is the structure of proinsulin?

A

Three chains - A chain, C peptide then B chain
2 disulphide bonds between chains A and B
1 disulphide bond at chain A

38
Q

What is the purpose of the disulphide bonds?

A

Between chains A and B - hold them together

At chain A - makes polypeptide curl up

39
Q

What is the structure of insulin?

A

No C peptide

so 2 polypeptide chains - A and B

40
Q

How is proinsulin modified in the Golgi?

A

C peptide is cleaved off

to produce insulin

41
Q

Where is the insulin transported to from the Golgi?

A

Buds off in vesicles from Golgi
vesicles marginate to cell surface
wait there

42
Q

What type of K+ channel do beta cells have on their cell membrane?

A

ATP sensitive K+ channels

43
Q

When do ATP sensitive K+ cells open and close?

A

Open with low ATP

Close when ATP is present - because they’re ATP sensitive duh

44
Q

When is insulin secreted by the beta cells?

A

When plasma glucose conc. is high

45
Q

How does high plasma glucose conc. lead to insulin secretion?

A 
high ATP levels inside beta cells
ATP sensitive K+ channels are shut
membrane depolarises
VGCCs open
influx of Ca2+
high intracellular Ca2+ conc. causes vesicles to fuse with plasma membrane
insulin and C peptide released
46
Q

What is the name of the process where vesicles fuse with the plasma membrane and release their contents?

A

Exocytosis

47
Q

Why is insulin not secreted when plasma glucose levels are low?

A

low ATP inside beta cells
ATP sensitive K+ channels are open
membrane hyperpolarises
VGCCs remain closed

48
Q

What does insulin bind to on target cells?

A

Insulin receptor

49
Q

What is the structure of the insulin receptor?

A

Dimer made up of two subunits

Each subunit is made up of

  • alpha chain
  • beta chain
50
Q

How does the insulin receptor sit in the plasma membrane?

A

Alpha chains are on exterior of plasma membrane

Beta chains are transmembrane

51
Q

How are the alpha and beta chains joined together to form one subunit?

A

By a single disulphide bond

52
Q

What are the target tissues of insulin?

A

Liver

Adipose tissue

Skeletal muscle

53
Q

Insulin affects the metabolism of…?

A

Carbohydrates - glycogen, glucose

Proteins

Lipids - TAGs, fatty acids

54
Q

What effect does insulin binding to insulin receptor on target cells in adipose tissue and skeletal muscle have?

A

Increases expression of GLUT4 protein on plasma membrane

giving increased uptake of glucose by those cells

55
Q

How does insulin affect plasma glucose levels therefore?

A

Decreases plasma glucose levels

56
Q

What effect does insulin binding to insulin receptor on target liver cells have?

A

Stimulates glycogenesis
Inhibits glycogenolysis

Inhibits gluconeogenesis

Inhibits breakdown of amino acids

57
Q

What effect does insulin binding to insulin receptor on target muscle cells have?

A

Increases uptake of amino acids

promoting protein synthesis

58
Q

What effect does insulin binding to insulin receptor on target adipose tissue cells have?

A

Increases storage of TAGs

Inhibits breakdown to fatty acids

59
Q

Does insulin have anabolic or catabolic effects? Why?

A

Anabolic

because it stimulates the synthesis of larger molecules from smaller ones

60
Q

How is insulin degraded?

A

Hormone-receptor complex is internalised by cell

insulin is broken down

61
Q

When is glucagon secreted?

A

When plasma glucose levels are low

62
Q

How is glucagon synthesised inside the cell?

A 
synthesised in ER
transported to Golgi
contained in budding vesicles
vesicles marginate to cell surface
wait there
contents released by exocytosis
63
Q

What is the structure of glucagon?

A

Single polypeptide chain

64
Q

What are the target tissues of glucagon? What is the main target tissue?

A

Liver - main target tissue

Adipose tissue

65
Q

Glucagon affects the metabolism of…?

A

Carbohyrates - glycogen, glucose

Lipids - TAGs, fatty acids

66
Q

How does glucagon affect target liver cells?

A

Stimulates glycogenolysis
Inhibits glycogenesis

Stimulates gluconeogenesis

67
Q

How does glucagon affect plasma glucose levels then?

A

Increases plasma glucose levels

68
Q

How does glucagon affect target adipose tissue cells?

A

Stimulates lipolysis

69
Q

So how does glucagon affect plasma fatty acid levels?

A

Increases plasma fatty acid levels

70
Q

Is glucagon anabolic or catabolic? Why?

A

Catabolic

Because is stimulating the breakdown of molecules to release energy

71
Q

If there is an increase in plasma amino acid levels, will there be a following increase in insulin or glucagon? Why?

A

Both!
Exact reason unknown
(but remember that in starvation protein stores are mobilised, increase in amino acid levels in blood, need glucagon for starvation)

72
Q

What are the rapid responses caused by insulin?

A

Glucose uptake in muscle, adipose tissue
Glycolysis

Amino acid uptake

73
Q

What are the intermediate responses caused by insulin?

A

Glycogenesis

Protein synthesis

74
Q

What are the delayed responses caused by insulin?

A

Lipogenesis

75
Q

What are the intermediate responses caused by glucagon?

A

Gluconeogenesis

Glycogenolysis

76
Q

What are the delayed responses caused by glucagon?

A

Lipolysis

Ketogenesis

Endocrinology (14 decks)

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