The Pancreas Endocrine Function Flashcards Preview

Metabolism, Endocrinology and Haematology > The Pancreas Endocrine Function > Flashcards

Flashcards in The Pancreas Endocrine Function Deck (13)
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1
Q

What types of hormones are produced in the pancreas and where are they produced

A

Polypeptide hormones

Islets of Langerhans

2
Q

What is the structure of insulin

A

Two polypeptide chains with two disulphide bonds covalently linking them

3
Q

How can we test for any endogenous insulin secretion

A

Measure plasma C-peptide

4
Q

How is insulin produced in beta-cells

A

Synthesised as pre-proinsulin and then enters endoplasmic reticulum where signal peptide, the pre part, is removed

Proinsulin is folded to ensure correct alignment of cysteine residues and is then transported to trans-golgi

It is packaged into storage vesicles and then undergoes proteolysis to removed connecting C-peptide, forming insulin

Storage vesicle then marginates to cell membrane

5
Q

How is insulin released from cells

A

Glucose enters cell via GLUT-2 and is metabolised to produce ATP

Increase in ATP close KATP channels in B-cell preventing K efflux

This depolarises the membrane, opening Ca channels

Ca enteres the cell causing the storage granules to fuse with the membrane and release their contents

6
Q

What are the major actions of insulin on metabolism

A

Increase glucose uptake by adipose and skeletal muscle (GLUT-4 channels inserted)

Increase glycogenesis and decrease glycogenolysis in liver and muscle

Decrease gluconeogenesis in liver

Increase glycolysis in liver and adipose

Decrease lipolysis in adipose

Increase lipogenesis and esterification of fatty acids in liver and adipose

Decrease ketogenesis in liver

Increase lipoprotein lipase activity in tissues

Increase amino acid uptake and protein synthesis in liver, muscle and adipose

Decrease proteolysis in liver, skeletal muscle and adipose

7
Q

What are the problems associated with abnormal levels of insulin and glucagon

A

Insulin

  • High - hypoglycaemia
  • Low - hyperglycaemia and diabetes mellitus

Glucagon

  • High - makes diabetes worse
  • Low - possibly contributes to hypoglycaemia
8
Q

What factors increase and what factors decrease insulin secretion

A

Stimulate - metabolic signals, GI tract hormones, acetyl choline

Inhibit - adrenaline, noradrenaline

9
Q

Describe the glucogen molecule and where it is produced

A

Single chain polypeptide

Lacks disulphide bonds and has a felxible 3D shape - takes up its active conformation on binding to its receptor

Produced by a-cells in Islets of Langerhans

10
Q

What factors control glucagon secretion

A

Stimulated by low plasma glucose

Inhibited by insulin and high/increase in plasma glucose

11
Q

What are the actions of glucagon

A

Increase glycogenolysis in liver

Increasde gluconeogenesis in liver

Decrease glycogenesis in liver

Increase ketogenesis in liver

Increase lipolysis in adipose

12
Q

When is glucagon used clinically

A

When a person with diabetes is experiencing hypoglycaemia and cannot take sugar orally

13
Q

What is the normal range of plasma glucose and what can it rise to after eating

A
  1. 3-6.0mmol/L normally
  2. 0-8.0mmol/L after a meal