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MEH > The Endocrine Pancreas > Flashcards

The Endocrine Pancreas Flashcards

1
Q

Where is the pancreas located and what shape is it?

A

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

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2
Q

What is the duodenal papilla (papilla of Vater)?

A

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

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3
Q

What are acini?

A

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

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4
Q

What do acini release into ducts?

A

Digestive enzymes
Bicarbonate ions

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5
Q

Which parts of the pancreas carry out the Endocrine function?

A

The Islets of Langerhans

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6
Q

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

A

Alpha
Beta
Delta

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7
Q

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

A

Insulin

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8
Q

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

A

Glucagon

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9
Q

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

A

Somatostatin

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10
Q

What types of hormones are Insulin and Glucagon?

A

Peptide hormones

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11
Q

What is the type of receptor for Insulin?

A

Tyrosine kinase

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12
Q

What type of receptor is the Glucagon receptor?

A

GPCR (G protein coupled receptor)

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13
Q

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

A

Anabolic affects

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14
Q

What does insulin stimulate?

A

Glucose oxidation
Glycogenesis
Lipogenesis
Protein synthesis

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15
Q

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

A

Activates GLUT4
Promotes its translocation

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16
Q

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

A

Catabolic affects

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17
Q

What does Glucagon stimulate?

A

Glycogenolysis
Gluconeogenesis
Lipolysis
Release of glucose from liver to blood

18
Q

What does Insulin inhibit?

A

Glycogenolysis
Gluconeogenesis
Lipolysis
Proteolysis

19
Q

Why does skeletal muscle not get affected by glucagon?

A

Has no glucagon receptors

20
Q

How many amino acids make up insulin?

A

51

21
Q

How many peptide chains make up Insulin?

A

2
1 alpha and 1 Beta chain

22
Q

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

A

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

23
Q

What is the Endocrine function of the pancreas?

A

To regulate blood glucose levels

24
Q

Where is insulin synthesised?

A

Beta cell

25
Q

What are the general steps in producing Insulin?

A

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

26
Q

How is insulin synthesised?
(Detail)

A

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

27
Q

How is C-peptide clinically relevant?

A

C peptide is released with insulin in equimolar amounts

Therefore it’s used to measure endogenous production/release of insulin from the pancreas

28
Q

Why is calcium important in exocytosis?

A

It binds to vesicles stimulating exocytosis

29
Q

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

A

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

30
Q

What happens to the B cell when plasma glucose increases?

A

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

31
Q

What is happening in a Beta cell at rest?

A

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

32
Q

What is meant by Insulin secretion being biphasic?

A

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

33
Q

How does insulin exert its affect on cells?

A

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

34
Q

What glucose transporter does insulin affect?

A

GLUT 4

35
Q

Where are GLUT 4 found?

A

Skeletal muscle
Adipose tissue

36
Q

Where is the main target of glucagon?

A

Liver

37
Q

How is glucagon synthesised?

A

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

38
Q

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

A

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

39
Q

How does glucagon release differ to Insulin release?

A

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

40
Q

How does Glucagon exert its effects on cells?

A

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

MEH (33 decks)

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