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SUGER > Endocrine Pancreas > Flashcards

Endocrine Pancreas Flashcards

1
Q

What forms the pancreas

A

At junction of foregut and midgut 2 pancreatic buds (dorsal and ventral) are generated and eventually fuse to form the pancreas

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2
Q

When does the exocrine function of the pancreas start

A

After birth

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3
Q

When does endocrine function begin

A

10-15 weeks

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4
Q

Location of pancreas

A

Retroperitoneal
Posterior to greater curvature of stomach

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5
Q

Length of pancreas

A

12-15cm

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6
Q

Where does the head of the pancreas sit

A

Near C-portion of duodenum

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7
Q

Acini

A

98-99% of cells are clusters

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8
Q

Which cells form exocrine activity

A

Acinar cells

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9
Q

Which cells perform endocrine activity

A

Islet cells

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10
Q

Exocrine activity

A

Manufacture and secrete fluid and digestive enzymes (pancreatic juice) which is released into the gut

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11
Q

Endocrine activity

A

Manufacture and release several peptide hormones into portal vein

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12
Q

What is the site of insulin and glucagon secretion

A

Islet of Langerhan’s

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13
Q

Alpha cells

A

Secrete glucagon

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14
Q

Beta cells

A

Secrete insulin

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15
Q

Percentage total volume of pancreas that is made up of islets of langerhans

A

2-3%

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16
Q

Delta cells

A

Secrete somatostatin

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17
Q

Paracrine crosstalk

A

Between Alpha and beta cells is physiological
I.e. local insulin release inhibits glucagon

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18
Q

How many amino acids make up insulin

A

51

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19
Q

Functions of insulin

A

Reduces glucose output by liver
Increases storage of glucose, fatty acids and amino acids

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20
Q

How many amino acids form glucagon

A

29

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21
Q

Function of glucagon

A

Mobilises glucose, fatty acids and amino acids from stores

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22
Q

What hormone stimulates the release of glucagon

A

Ghrelin

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23
Q

What hormone inhibits gastric emptying

A

Pancreatic polypeptide

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24
Q

Function of somatostatin

A

Inhibitor

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25
Counterregulatory hormes of insulin
Glucagon Adrenaline Cortisol Growth hormone
26
What does insulin suppress
Hepatic glucose output Decrease Glycogenolysis and gluconeogenesis Lipolysis Breakdown of muscle (decreased ketogenesis)
27
What does insulin increase
Glucose uptake by insulin sensitive tissue Muscles- glycogen and protein synthesis Fat- fatty acid synthesis
28
Glucagon increases
Hepatic glucose output- increases Glycogenolysis and gluconeogenesis Stimulates peripheral release of gluconeogenic precursors (glycerol and amino acids) -lipolysis -muscle Glycogenolysis and breakdown
29
Glucagon reduces
Peripheral glucose uptake
30
Which hormone increase Glycogenolysis and gluconeogenesis
Glucagon
31
Which hormone decrease Glycogenolysis and gluconeogenesis
Insulin
32
Insulin secretion by the beta cell
Glucose enters by GLUT2 glucose transporter Glucose is phosphorylated by glucokinase —> glucose-6-phosphate Glucose metabolism —> increase ATP present Closes K+ channel —> depolarises membrane Voltage gated Ca2+ channels opens and Ca2+ influx Mobilisation of insulin secretory granules and release of insulin by exocytosis
33
GLUT2
Low affinity transporter
34
Proinsulin
contains the A and B chains of insulin (21 and 30 amino acid residues respectively), joined by the C peptide. Disulfide bridges link a and B chains Presence of C peptide implies endogenous insulin production
35
What form is insulin secreted in
Proinsulin
36
What type of bond links A and B insulin chains
Disulphide bridges
37
Proinsulin is composed of
Insulin and C-peptide
38
What does presence of C peptide imply
Endogenous insulin production
39
Biphasic insulin release
B-cells sense rising glucose and aim to metabolise it 1st. Rapid release of stored product 2. Response is slower and it is the release of newly synthesised hormone
40
Insulin action in muscle and fat cells
Insulin receptor Intracellular signaling cascades Intracellular GLUT4 vesicles GLUT4 vesicle mobilisation to plasma membrane and integration into membrane Glucose entry into cells via GLUT4
41
What organ is a short-term glucose buffer
Liver
42
Normal blood glucose
5 mmol/mol
43
Blood glucose is too high
>6 mmol/mol
44
Short term response to high glucose
Glycogenesis
45
Long term response to high blood glucose
Lipogenesis
46
Low blood glucose
<4 mmol/mol
47
Short term response to low blood glucose
Glycogenolysis
48
Long term response to low blood glucose
Gluconeogenesis
49
Where are primary glucose sensors
Pancreatic islets
50
Glucose sensing- other than islets
Also in medulla, hypothalamus and carotid bodies Inputs from eye, nose, taste buds, gut all involved in regulating food Sensory cells in gut wall also stimulate insulin release from pancreas - incretins
51
Incretins
Gut hormones stimulating insulin release are called incretins, glucagon-like peptide (GLP-1) and glucose-dependent insulinotrophic peptide(GIP)
52
When is insulin response greater
Following oral glucose than intravenous glucose despite similar plasma glucose concentrations
53
Mechanism of incretins
Increase insulin Decrease glucagon Delays gastric emptying
54
GLP-1
Glucose dependent and short half life Dipeptidyl peptidases IV cleaves GLP-1 Half-life of GLP-1 = 1-2 mins DPP-IV prevents hypoglycaemia
55
Half life of GLP-1
1-2 mins - prevents hypoglycaemia
56
In fasting state where does glucose come from
Liver- Breakdown of glycogen -gluconeogenesis
57
What are the precursors for gluconeogenesis
Lactate Alanine Glycerol
58
What do muscles use for fuel in fasting state
Free fatty acids
59
Post prandial
After feeding
60
What percentage of ingested glucose goes to liver
40%
61
What percentage of ingested glucose goes to periphery (mostly muscle)
60%
62
After feeding
physiological need to dispose of a nutrient load Rising glucose (5-10 min after eating) stimulates 5-10 fold increase in insulin secretion and suppresses glucagon
63
What is excess glucose converted into
Fats
64
What does high insulin and glucose levels suppress
lipolysis and levels of non-esterified fatty acids (NEFA or FFA) fall
65
What stimulates release of glucagon
Hypoglycaemia
66
Action of glucagon on liver
Glycogenolysis Gluconeogenesis from lactate and amino acids
67
What inhibits release of glucagon
Hyperglycaemia
68
What stimulates release of insulin
Hyperglycaemia
69
Actions of insulin
Accelerate facilitated diffusion of glucose into cells Speed conversion of glucose into glycogen Increase uptake of amino acids and increase protein synthesis Speed synthesis of fatty acids Slow glycogenolysis Slow gluconeogenesis
70
What inhibits insulin release
Hypoglycaemia
71
Diabetes mellitus
Disorder of carbohydrate metabolism characterised by hyperglycaemia
72
Mechanism of diabetes mellitus type 2
Mutation in K+ (ATP activated) channels so remains open longer than it should —> need higher blood glucose in order for insulin secretion
73
What can treat type 2 diabetes
Sulphonylureas Synthetic incretins
74
Synthetic incretins
Synthetic incretins Stimulates insulin secretion which lowers blood glucose and decreases gastric emptying by acting as DDP-IV inhibitiors
75
Action of sulphonylureas
Potassium channel closes and depolarises cell membranes
76
Pathogenesis of diabetic ketoacidosis - no hepatic insulin effect
Unrestrained glucose and ketone production - more glucose enters blood - hyperglycaemia and raised plasma ketones - glycosuria/ketonuria
77
Pathogenesis of diabetic ketoacidosis- no muscle/fat insulin effect
Impaired glucose clearance and muscle/fat breakdown - less glucose enters peripheral tissues -hyperglycaemia and raised plasma ketones - glycosuria/ketonuria
78
Pathogenesis of diabetic ketoacidosis - absent insulin secretion
No hepatic insulin effect No muscle/fat insulin effect
79
A 13 year old boy is prescribed insulin as a treatment for his Type I diabetes mellitus. Which of the following metabolic processes is upregulated by insulin?
Expression of GLUT4 in muscle cells
80
What stimulates release of incretins
Endothelial cells in gut in response to to eating
81
Action of incretins
Amplifies insulin response to glucose
82
Incretins examples
Glucagon-like peptide 1 Glucose dependent insulinotrophic peptide 1
83
What binds to insulin secretory granules causing their release
Ca2+
84
Mechanism of insulin release
GLUT2 on beta cells has low affinity for glucose When glucose is HIGH, enters cell Undergoes metabolism to produce glucose-6-phosphate ATP then acts on KATP channels and inactivates them Membrane depolarises Ca2+ voltage gated channels open so influx of Ca2+ Binds to secretory granules causing release
85
What does the conversion of glucose to glucose-6-phosphate require
ADP and hexokinase

SUGER (17 decks)

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