Pancreas

Question 1

How does the pancreas develop?

Answer 1

Embryologically as an outgrowth of the foregut

Question 2

Describe the structure of the pancreas and their corresponding functions

Answer 2

Acinar cells - exocrine function
Islets of Langerhans - endocrine function

Question 3

Outline the exocrine function of the pancreas

Answer 3

Acinar cells - secrete digestive enzymes
Ductal cells - secrete bicarbonate ions

Question 4

What digestive enzymes are produced by the pancreas?

Answer 4

Proteases - trypsin + chymotrypsin
Pancreatic lipases
Pancreatic amylase

Question 5

Major cells in the Islets of Langerhans and what they secrete

Answer 5

Beta cells - insulin
Alpha cells - glucagon
Delta cells - somatostatin

Question 6

Actions of insulin

Answer 6

Anabolic
- increases glucose oxidation
- increases glycogen synthesis
- increases fat synthesis
- increases protein synthesis

Question 7

Action of glucagon

Answer 7

Catabolic
- increases glycogenolysis
- increased gluconeogenesis
- increased ketogenesis

Question 8

What does insulin act on?

Answer 8

Liver
Adipose
Skeletal muscle

Question 9

What does glucagon act on?

Answer 9

Liver
Adipose
NOT skeletal muscle - lacks glucagon receptors

Question 10

How does insulin increase glucose uptake?

Answer 10

Promotes GLUT4 translocation in adipose + skeletal muscle

Question 11

Describe insulin

Answer 11

Peptide hormone
Made of 2 in branched chains held together by 2 disulphide bonds
a-helix structure

Question 12

Outline insulin synthesis

Answer 12

DNA in B cell > mRNA > preproinsulin > proinsulin > insulin + C-peptide (cleaved off to leave insulin)

1- preproinsulin synthesised in nucleus of B cells
2- PPI sent to rough ER
3- PPI cleaved to proinsulin
4- PI folded + disulphide bridges are formed
5- PI transported to Golgi apparatus
6- PI cleaved to give insulin + C peptide
7- packaged into secretory granules for release

Question 13

What is C peptide used for?

Answer 13

Clinical marker of synthesis of insulin

Question 14

Outline insulin secretion

Answer 14

1- increase in blood glucose conc.
2- glucose enters B cells via GLUT2 transporter
3- increase in glycolysis > increase in ATP
4- increase in ATP:ADP ratio
5- ATP dependent K+ channels close
6- depolarisation
7- VGCC open > influx of Ca2+
8- secretory granules released via exocytosis

Question 15

What stimulates insulin release?

Answer 15

Parasympathetic nervous system

• increased plasma glucose, aa and free fatty acids
• glucagon
• adrenaline at B cell receptor

Question 16

What inhibits insulin release?

Answer 16

Sympathetic nervous system

• decrease in plasma glucose, aa + free fatty acids
• somatostatin
• Leptin
• adrenaline at a cell receptor

Question 17

How does insulin exert its effect on cells?

Answer 17

1- insulin binds to insulin receptor (tyrosine kinase)
2- receptor auto-phosphorylation
3- activation of signally complexes at cell membrane 4- has effects on metabolic pathways + glucose uptake

Question 18

Describe the structure of glucagon

Answer 18

Peptide horomone
No disulphide bonds

Question 19

Outline glucagon synthesis

Answer 19

DNA > mRNA > preproglucgaon > proglucagon > glucagon

Question 20

How does glucagon exert its effect on cells?

Answer 20

1- glucagon binds to glucagon receptor (GPCR)
2- G protein activation
3- effector protein activation
4- 2nd messenger formation
5- effects on metabolic pathways + gene expression

Question 21

What is the half life of insulin and glucagon in plasma?

Answer 21

5 minutes

Question 22

What type of receptor is an insulin recpeotr?

Answer 22

Tyrosine kinase

Question 23

What type of receptor are glucagon receptor?

Answer 23

GPCR

Question 24

Describe type 1 diabetes mellitus

Answer 24

Absolute insulin deficiency caused by autoimmune destruction of pancreatic B cels

Question 25

Describe type 2 diabetes mellitus

Answer 25

Relative insulin deficiency casued by insulin resistance