S10) The Endocrine Pancreas Flashcards Preview

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Flashcards in S10) The Endocrine Pancreas Deck (33)
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1

Describe the two functions of the pancreas

- Produces digestive enzymes (exocrine action ~99%)

- Hormone production (endocrine action ~1%)

2

Important polypeptide hormones are secreted by the pancreas.

Identify them

- Insulin

- Glucagon

- Somatostatin

- Pancreatic polypeptide

- Ghrelin

- Gastrin

- Vasoactive intestinal peptide 

3

Identify the seven main cell types in pancreatic islets

β cells – Insulin

- α cells – Glucagon

- d cells – Somatostatin

- PP cells – Pancreatic polypeptide

- e cells – Ghrelin

- G cells – Gastrin

- VIP

4

Describe the role of insulin and glucagon

Insulin & Glucagon – regulation of metabolism of carbohydrates, proteins, and fats 

5

Both insulin and glucagon are controllers of plasma glucose.

Describe their respective functions

- Insulin – lowers blood glucose levels

- Glucagon – raises blood glucose levels 

6

Compare and contrast the metabolic actions of insulin and glucagon in terms of the following:

- Onset

- Target tissues

- Affected metabolism

- Actions

7

Describe how the measured plasma glucose concentration may vary

Normally: 3.3-6 mmol/L

- After a meal: 7-8 mmol/L

- Renal threshold: 10 mmol/L (≥ glycosuria)

8

Describe the shared properties of insulin and glucagon in terms of the following:

- Solubility

- Transport

- Half life

- Receptors

- Inactivation

- Solubility  water soluble hormones

- Transport – transported dissolved in plasma

- T½ – 5 mins (short)

- Receptors – cell surface receptors on target cells

- Inactivation – receptor-hormone complex can be internalised 

9

Insulin is the hormone of energy storage.

In light of this, state four of its unique properties

Insulin favours energy storage:

- Anabolic

- Anti-gluconeogenic

- Anti-lipolytic

- Anti-ketogenic

10

Describe the structure of insulin

- Insulin is a large polypeptide with an alpha helix structure

- It is composed of 2 un-branched peptide chains, connected by 2 disulphide bridges for stability 

11

Outline the synthesis and secretory pathway of insulin

12

Explain the metabolic regulation of KATP channels and insulin secretion

13

Insulin binds to the insulin receptor on cell surfaces.

Describe the properties of the insulin receptor

Insulin receptor is a dimer, connected together by a single di-sulphide bond:

- α-chain on exterior of the cell membrane

- β-chain spans the cell membrane in a single segment

14

How does insulin increase glucose uptake into target cells and glycogen synthesis?

Insertion of Glut 4 channel

15

Describe the effects of insulin-uptake on metabolism in the following tissue locations:

- Liver

- Muscles

- Adipose tissue

- Liver – increases glycogen synthesis and inhibits breakdown of amino acids

- Muscles –  increase uptake of amino acids promoting protein synthesis

- Adipose tissue – increases the storage of triglycerides and inhibits breakdown of fatty acids 

16

Glucagon is the hormone of energy mobilisation.

In light of this, state four of its unique properties

Glucagon favours energy mobilisation:

- Catabolic

- Gluconeogenic

- Lipolytic

- Ketogenic

17

Describe the structure of glucagon

- 29 amino acids in 1 polypeptide chain

- No disulphide bridges i.e. flexible structure 

18

Glucagon is secreted due to low glucose levels in α-cells.

In 5 steps, outline in synthesis and secretory pathway

⇒ Synthesised in rER

⇒ Transported to Golgi

⇒ Packaged in granules

⇒ Storage granules move to cell surface (margination)

⇒ Exocytosis – fusion of vesicle membrane with plasma membrane with the release of the vesicle contents

19

Describe the effects of glucagon-uptake on metabolism in the following tissue locations:

- Liver

- Adipose tissue

- Liver – increases the rate of glycogenolysis and stimulates pathway for gluconeogenesis from amino acids

- Adipose tissue – stimulates lipolysis to increase plasma fatty acid 

20

Describe the net effects of glucagon and insulin on carbohydrate metabolism as well as their relative speed

21

Describe the net effects of glucagon and insulin on lipid metabolism as well as their relative speed

22

Describe the net effects of glucagon and insulin on amino acid metabolism as well as their relative speed

23

What happens when insulin and glucagon levels are abnormal?

Insulin:

I. High – hypoglycaemia

II. Low – hyperglycaemia (diabetes mellitus)

- Glucagon:

I. High – worsens diabetes

II. Low – may contribute to hypoglycaemia 

24

Diabetes Mellitus is a group of metabolic disorders resulting from abnormal insulin levels. 

What is it characterised by?

- Chronic hyperglycaemia

- Long-term clinical complications

- Elevated glucose levels in urine 

25

How is Diabetes Mellitus diagnosed?

Diagnosis is based on venous plasma glucose concentration:

- Fasting ≥ 7.0mM

- Random ≥ 11.1mM 

26

What is the cause of Diabetes in Type I Diabetes Mellitus?

Type I – absolute insulin deficiency due to the autoimmune destruction of Pancreatic β- cells

27

What is insulin deficiency?

Insulin deficiency is the failure to secrete adequate amounts of insulin from β-cells  

28

What are the two types of insulin deficiency?

Absolute – destruction of pancreatic β- cells

- Relative – abnormally slow/small secretory response of β-cells

29

What change occurs in KATP channels in relative insulin deficiency?

30

What is the cause of Diabetes in Type II Diabetes Mellitus?

Type 2 – normal insulin secretion but relative peripheral insulin resistance