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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
What is the renal threshold of glucose?
10mmol/L
26
What is glycosuria?
Glucose in the urine
27
When is the renal threshold of glucose increased?
Elderly
28
When is the renal threshold of glucose decreased?
Pregnancy
29
When is insulin released?
When plasma glucose is high
30
How do insulin and glucagon react to water?
Hydrophilic | Water-soluble
31
What is the advantage of insulin and glucagon being water-soluble?
Can dissolve in plasma | No special transport proteins required
32
What is the half life of insulin and glucose? What is the advantage of this?
5 minutes Have short-lived effects Useful because plasma glucose conc. is always changing
33
Where is insulin synthesised in the pancreatic beta cell?
ER
34
What form of insulin is synthesised in the ER?
Preproinsulin
35
How is preproinsulin modified in the ER?
Cleaved | to produce proinsulin
36
Where is proinsulin transported to from the ER?
Golgi
37
What is the structure of proinsulin?
Three chains - A chain, C peptide then B chain 2 disulphide bonds between chains A and B 1 disulphide bond at chain A
38
What is the purpose of the disulphide bonds?
Between chains A and B - hold them together At chain A - makes polypeptide curl up
39
What is the structure of insulin?
No C peptide | so 2 polypeptide chains - A and B
40
How is proinsulin modified in the Golgi?
C peptide is cleaved off | to produce insulin
41
Where is the insulin transported to from the Golgi?
Buds off in vesicles from Golgi vesicles marginate to cell surface wait there
42
What type of K+ channel do beta cells have on their cell membrane?
ATP sensitive K+ channels
43
When do ATP sensitive K+ cells open and close?
Open with low ATP Close when ATP is present - because they're ATP sensitive duh
44
When is insulin secreted by the beta cells?
When plasma glucose conc. is high
45
How does high plasma glucose conc. lead to insulin secretion?
``` 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
What is the name of the process where vesicles fuse with the plasma membrane and release their contents?
Exocytosis
47
Why is insulin not secreted when plasma glucose levels are low?
low ATP inside beta cells ATP sensitive K+ channels are open membrane hyperpolarises VGCCs remain closed
48
What does insulin bind to on target cells?
Insulin receptor
49
What is the structure of the insulin receptor?
Dimer made up of two subunits Each subunit is made up of - alpha chain - beta chain
50
How does the insulin receptor sit in the plasma membrane?
Alpha chains are on exterior of plasma membrane Beta chains are transmembrane
51
How are the alpha and beta chains joined together to form one subunit?
By a single disulphide bond
52
What are the target tissues of insulin?
Liver Adipose tissue Skeletal muscle
53
Insulin affects the metabolism of...?
Carbohydrates - glycogen, glucose Proteins Lipids - TAGs, fatty acids
54
What effect does insulin binding to insulin receptor on target cells in adipose tissue and skeletal muscle have?
Increases expression of GLUT4 protein on plasma membrane | giving increased uptake of glucose by those cells
55
How does insulin affect plasma glucose levels therefore?
Decreases plasma glucose levels
56
What effect does insulin binding to insulin receptor on target liver cells have?
Stimulates glycogenesis Inhibits glycogenolysis Inhibits gluconeogenesis Inhibits breakdown of amino acids
57
What effect does insulin binding to insulin receptor on target muscle cells have?
Increases uptake of amino acids | promoting protein synthesis
58
What effect does insulin binding to insulin receptor on target adipose tissue cells have?
Increases storage of TAGs Inhibits breakdown to fatty acids
59
Does insulin have anabolic or catabolic effects? Why?
Anabolic | because it stimulates the synthesis of larger molecules from smaller ones
60
How is insulin degraded?
Hormone-receptor complex is internalised by cell | insulin is broken down
61
When is glucagon secreted?
When plasma glucose levels are low
62
How is glucagon synthesised inside the cell?
``` synthesised in ER transported to Golgi contained in budding vesicles vesicles marginate to cell surface wait there contents released by exocytosis ```
63
What is the structure of glucagon?
Single polypeptide chain
64
What are the target tissues of glucagon? What is the main target tissue?
Liver - main target tissue Adipose tissue
65
Glucagon affects the metabolism of...?
Carbohyrates - glycogen, glucose Lipids - TAGs, fatty acids
66
How does glucagon affect target liver cells?
Stimulates glycogenolysis Inhibits glycogenesis Stimulates gluconeogenesis
67
How does glucagon affect plasma glucose levels then?
Increases plasma glucose levels
68
How does glucagon affect target adipose tissue cells?
Stimulates lipolysis
69
So how does glucagon affect plasma fatty acid levels?
Increases plasma fatty acid levels
70
Is glucagon anabolic or catabolic? Why?
Catabolic | Because is stimulating the breakdown of molecules to release energy
71
If there is an increase in plasma amino acid levels, will there be a following increase in insulin or glucagon? Why?
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
What are the rapid responses caused by insulin?
Glucose uptake in muscle, adipose tissue Glycolysis Amino acid uptake
73
What are the intermediate responses caused by insulin?
Glycogenesis Protein synthesis
74
What are the delayed responses caused by insulin?
Lipogenesis
75
What are the intermediate responses caused by glucagon?
Gluconeogenesis Glycogenolysis
76
What are the delayed responses caused by glucagon?
Lipolysis Ketogenesis

Endocrinology (14 decks)

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