The Endocrine Pancreas

Question 1

Where is the pancreas located and what shape is it?

Answer 1

Head of pancreas tucked in the curvature of the duodenum
Fish shaped

Question 2

What is the duodenal papilla (papilla of Vater)?

Answer 2

The part by which digestive enzymes and bicarbonate from the pancreas enter the duodenum

Question 3

What are acini?

Answer 3

Clusters of cells that carry out the exocrine function of the pancreas

Question 4

What do acini release into ducts?

Answer 4

Digestive enzymes
Bicarbonate ions

Question 5

Which parts of the pancreas carry out the Endocrine function?

Answer 5

The Islets of Langerhans

Question 6

What are the 3 main cells in the islets of Langerhans?

Answer 6

Alpha
Beta
Delta

Question 7

What hormone do Beta cells of the Islets of Langerhans produce?

Answer 7

Insulin

Question 8

What hormone do the Alpha cells of the islets of Langerhans produce?

Answer 8

Glucagon

Question 9

What hormone do the Delta cells of the islets of Langerhans produce?

Answer 9

Somatostatin

Question 10

What types of hormones are Insulin and Glucagon?

Answer 10

Peptide hormones

Question 11

What is the type of receptor for Insulin?

Answer 11

Tyrosine kinase

Question 12

What type of receptor is the Glucagon receptor?

Answer 12

GPCR (G protein coupled receptor)

Question 13

What is the general affect Insulin has on the Liver, Adipose tissue and Skeletal muscle?

Answer 13

Anabolic affects

Question 14

What does insulin stimulate?

Answer 14

Glucose oxidation
Glycogenesis
Lipogenesis
Protein synthesis

Question 15

How does Insulin affect GLUT4 in skeletal muscles and Adipose tissue?

Answer 15

Activates GLUT4
Promotes its translocation

Question 16

What affect does Glucagon have on the Liver and Adipose tissue?

Answer 16

Catabolic affects

Question 17

What does Glucagon stimulate?

Answer 17

Glycogenolysis
Gluconeogenesis
Lipolysis
Release of glucose from liver to blood

Question 18

What does Insulin inhibit?

Answer 18

Glycogenolysis
Gluconeogenesis
Lipolysis
Proteolysis

Question 19

Why does skeletal muscle not get affected by glucagon?

Answer 19

Has no glucagon receptors

Question 20

How many amino acids make up insulin?

Answer 20

51

Question 21

How many peptide chains make up Insulin?

Answer 21

2
1 alpha and 1 Beta chain

Question 22

How are the Alpha and Beta chain held together in Insulin?

Answer 22

2 disulphide bonds between the chains
1 Intra-chain bond in the Alpha chain

Question 23

What is the Endocrine function of the pancreas?

Answer 23

To regulate blood glucose levels

Question 24

Where is insulin synthesised?

Answer 24

Beta cell

Question 25

What are the general steps in producing Insulin?

Answer 25

DNA in B cell transcripted mRNA translated Preproinsulin Proinsulin Insulin and C-peptide

Question 26

How is insulin synthesised? (Detail)

Answer 26

Preproinsulin is produced and enters the ER Signal peptide is cleaved off forming the Proinsulin Proinsulin enters the Golgi apparatus Proinsulin is cleaved in vesicle form in the active Insulin peptide and C-peptide

Question 27

How is C-peptide clinically relevant?

Answer 27

C peptide is released with insulin in equimolar amounts Therefore it’s used to measure endogenous production/release of insulin from the pancreas

Question 28

Why is calcium important in exocytosis?

Answer 28

It binds to vesicles stimulating exocytosis

Question 29

What are the 3 important transporters in a Beta cell needed for insulin release?

Answer 29

GLUT 2 ATP sensitive potassium ion (K+) channel Voltage gated Ca2+ channel

Question 30

What happens to the B cell when plasma glucose increases?

Answer 30

GLUT2 allows more glucose into B cell Increased rate of Glycolysis increasaes ATP levels in cell ATP inhibits ATP sensitive K+ channels so K+ can’t leave cell Cell depolarises This activates Ca2+ voltages gated ion channels causing an influx in Ca2+ in cell Ca2+ binds to secretory vesicles causing them to release insulin and C peptide via exocytosis

Question 31

What is happening in a Beta cell at rest?

Answer 31

Less glucose transported in via GLUT2 Low ATP concentration in cell K+ channels stay open and K+ can leave the cell Cell stays with a negative membrane potential Voltage gated Ca2+ ion channels stay closed

Question 32

What is meant by Insulin secretion being biphasic?

Answer 32

There is a rapid initial burst of insulin released A drop Then a gradual increase in insulin

Question 33

How does insulin exert its affect on cells?

Answer 33

Binds to its Tyrosin Kinase receptor Receptor Phosphorylates itself (becomes negatively charged) This activates and recruits signalling complexes at the cell membrane These signalling complexes effect metabolic pathways and glucose uptake

Question 34

What glucose transporter does insulin affect?

Answer 34

GLUT 4

Question 35

Where are GLUT 4 found?

Answer 35

Skeletal muscle Adipose tissue

Question 36

Where is the main target of glucagon?

Answer 36

Liver

Question 37

How is glucagon synthesised?

Answer 37

Preproglucagon (signal peptide cleaved in ER) Proglucagon (proteolytically processed cleaving the peptide in the Golgi apparatus) Glucagon and other peptide hormones

Question 38

What are the 3 transporters important in glucagon release in an alpha cell?

Answer 38

GLUT 1 ATP sensitive K+ channel Voltage gated Ca2+ channel

Question 39

How does glucagon release differ to Insulin release?

Answer 39

In glucagon release, the ATP sensitive K+ ion channel closes when [ATP] is low Whereas in insulin release, the ATP sensitive K+ ion channel closes when [ATP] is high

Question 40

How does Glucagon exert its effects on cells?

Answer 40

Glucagon binds to glucagon receptor G protein activates Effector protein activates (adenyly cyclase) 2nd messenger is formed (cAMP) cAMP effects metabolic pathways and gene expression