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MEH > 10. Pancreas > Flashcards

10. Pancreas Flashcards

1
Q

What is the embryological origin of the pancreas?

A

Outgrowth of the foregut

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2
Q

What proportion of the pancreas is responsible for exocrine secretions?

A

99%

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3
Q

What is the exocrine function of the pancreas?

A

Secretion of digestive enzymes and alkaline secretions into the duodenum.

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4
Q

What 2 hormones are released by the endocrine pancreas?

A

Insulin

Glucagon

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5
Q

Which cells are responsible for insulin secretion?

A

Beta cells (75%)

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6
Q

Which cells are responsible for glucagon secretion?

A

Alpha cells (25%)

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7
Q

What name is given to the regions of the pancreas that contain endocrine cells?

A

Islets of langerhans

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8
Q

What signals insulin release?

A

Feeding - glucose

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9
Q

What signals glucagon release?

A

Fasting

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10
Q

What are the target tissues for insulin?

A

Liver, adipose, skeletal muscle

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11
Q

How do the target tissues of glucagon differ to those of insulin?

A

Glucagon doesn’t have an effect on skeletal muscle

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12
Q

Which pancreatic hormone is considered anabolic?

A

Insulin

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13
Q

What is the normal plasma glucose range?

A

3.3-6 mmol/L

After a meal 7-8 mmol/L

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14
Q

What is the renal threshold for glucose?

A

10mmol

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15
Q

What happens if glucose levels rise above the renal threshold?

A

Glucosuria

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16
Q

How does the renal threshold alter in pregnant patients and elderly patients?

A

Pregnancy - decreases

Elderly - increases

17
Q

Why is it so important to tightly regulate plasma glucose levels?

A

Energy supply - brain uses glucose at a fast rate and is sensitive to depletion
Osmolarity of plasma

18
Q

What type of hormones are insulin and glucagon, how does this determine their transport in the blood?

A

Peptide hormones

Water soluble - no transport needed

19
Q

Which pancreatic hormone is anabolic?

A

Insulin

20
Q

Outline the structure of insulin.

A

2 peptide chains connected by 3 disulphide bonds

21
Q

What structural feature of insulin confers stability?

A

Disulphide bonds

22
Q

What occurs in insulin storage vesicles prior to release, how is this clinically useful?

A

Proteolysis to produce insulin + C-peptide in equal amounts. Plasma C-peptide can be used to measure levels of endogenous insulin secretion.

23
Q

How much of it’s insulin stores does the pancreas secrete each day?

A

Only 15% - rest is stored

24
Q

Which ion channel is present on the beta-cell membrane which controls insulin secretion?

A

ATP sensitive - K+ channel

25
Q

How does the ATP K+ channel regulate insulin secretion?

A

When glucose levels are high, it enters the beta cell and enters glycolysis to produce ATP.
ATP binds to the K+ channel, inactivating it.
Hyper polarisation of the cell opens volatage-gated calcium channels.
Calcium influx triggers exocytosis of vesicles.

26
Q

What type of receptor is the insulin receptor?

A

Tyrosine kinase - alpha and beta chain

27
Q

How does insulin alter glucose uptake in target cells?

A

Inserts GLUT4 transporter to cell membranes to increase glucose uptake.
Increases glycogen synthesis

28
Q

What effect does insulin have on muscle tissue?

A

Increased uptake of amino acids, increased protein synthesis.

29
Q

What effect does insulin have on adipose tissue?

A

Increases lipogenesis and TAG storage.

30
Q

How does the structure of glucagon compare to that of insulin?

A

Peptide hormone but a single chain with no disulphide bonds.

31
Q

What are the main actions of glucagon?

A

Increase glycogenolysis, gluconeogenesis, ketogenesis and lipolysis.

32
Q

What receptor type does glucagon bind to?

A

GPCR - alpha s

33
Q

The half-life of insulin in plasma is approximately?

A

5 minutes - relatively short half life to respond rapidly to changes in glucose concentration.

34
Q

How many disulphide bonds are there in insulin?

A

3 in total: 2 link the A and B chains

1 bond within A chain

35
Q

What properties of C-peptide make it such a useful clinical marker?

A

it has a longer half life and so is more stable than insulin in plasma

36
Q

Which glucose transporter is the primary transporter of glucose in pancreatic β cells?

A

GLUT2

37
Q

Where else is GLUT2 important?

A

Liver - bi-directional so allows glucose release from gluconeogenesis as well as absorption

38
Q

What is the medical term used to describe excessive thirst?

A

Polydipsia

MEH (19 decks)

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