L27 Regulation Of Glucose

Question 1

What are the 3 main islet secretory cells?

Answer 1

1. β (65%)
2. α (20%)
3. Delta (10%)

Question 2

What does the beta and alpha cells of endocrine pancreas secrete?

Answer 2

β cells – insulin (peptide hormone), proinsulin, C peptide, amylin (IAPP)
α cells – glucagon

Question 3

What does δ and f cells in endocrine tissue secrete?

Answer 3

δ cells – somatostatin
F (PP) cells – pancreatic polypeptide

Question 4

What do ε cells produce?

Answer 4

Ghrelin protein

Question 5

Give me examples of endocrine cells (5

Answer 5

ε cells
δ cells (delta)
β cells (beta)
α (cells (alpha
F (PP) cells

Question 6

How are islets of langerhans perfused?

Answer 6

1. Small arteries enter islet core and distribute blood through the fenestrated capillaries.
2. Through vascular arrangement - venous blood of one cell type bathes the others.
3. Richly perfused blood metabollically activate, releases hormone and sense nutrients.

Question 7

How do the endocrine cells communicate to each other?

Answer 7

• Via gap junctions between the beta and alpha
  Delta cells send dendrite-like processes to beta cells

Question 8

The islets of Langerhans receive nerve signals from which types of neurones?

Answer 8

Adrenergic
Cholinergic
(Peptidergic neurons)

Question 9

Describe how insulin secretion is regulated

Answer 9

1) High blood glucose stimulates insulin syntehsis + secretion, low levels inhibit
2) Neural control - Parasympathetic nervous system stimulates insulin secretion, sympathetic inhibits insulin
3) Humoral factors - GIP, Amylin, Somatostatin
4) Drugs

Question 10

What is the mechanism of secretion in the beta cells of pancreas?

Answer 10

1. Glucose enters beta cell through GLUT2 and is metabolized through glycosis and oxidative phosphorylation which increases ATP levels
2. Increased ATP levels results the closing of KATP channels preventing outflow of K+
3. Reduced outflow of K+ = buildup of positive charge inside the cell, causing membrane potential to depolarise
4. Depolarisation opens voltage-gated calcium channels
5. Calcium ions enter and secrete out insulin through exocytosis.

Question 11

Receptor activation initiates a cascade of phoshporylation events that may activate or inhibit what? (4)

Answer 11

• PKC
• Phosphatases
• Phospholipases
• G proteins

Range of downstream effects - cell grwoth, proliferation, gene expression

Question 12

What does down regulated mean?

Answer 12

The cell becomes less responsive to insulin which can happen when receptors become less sensitive to insulin

Question 13

What are the two brief effects of insulin action?

Answer 13

• Decreases blood glucose concentration
• Increased glucose transport into target cells by insertion of GLUT4

Question 14

Which body cells are mainly targeted by endocrine hormones?

Answer 14

Liver + muscle tissues are targeted to store glucose as glycogen

Question 15

What is glycogenesis?

Answer 15

Conversion of glucose to glycogen

Question 16

What is lipogenesis?

Answer 16

Excess glucose converted into fat

Question 17

Do insulin have a stimulatory and an inhibitory effect?

Answer 17

Stimulates formation of glycogen from glucose (glycogenesis)
Inhibits glycogenolysis
Inhibits gluconeogensis

Question 18

What are the 4 major muscle effects that the actions of insulin have?

Answer 18

1) Increased glucose uptake
2) Promotes glycogen synthesis
3) Promotes glycolysis and carbohydrate oxidation
4) Promotes protein synthesis

Question 19

What are adipocytes?

Answer 19

Fat cells that store energy in the form of triglycerides (fats)

Question 20

What does Lipoprotein lipase (LPL) do?

Answer 20

It’s an enzyme that breaks down triglycerides and releases FA

Question 21

What do insulin do to adipocytes?

Answer 21

Insulin generally inhibits lipolysis in adipocytes

Question 22

What is lipolysis?

Answer 22

Metabolic process by which triglycerides (fats) are broken down into glycerol and free fatty acids

Question 23

What effects do insulin have on Na+/K+ pumps?

Answer 23

Promotes K+ uptake into cells through increased activity of N+/K+ ATPase

Direct effect on hypothalamic satiety centre

Question 24

What is diabetes mellitus?

Answer 24

A group of metabolic disorder characterised by high blood sugar levels over a prolonged period

Question 25

What is type 1 diabetes?

Answer 25

Where the body’s immune system destroys the pancreatic insulin- producing cells

Question 26

What is type 2 diabetes?

Answer 26

The body doesn’t produce enough insulin because the receptors don’t respond to the insulin (resistance receptors)

Question 27

What are the biological effects of type 1 diabetes mellitus? (8)

Answer 27

• Secrete inadequate insulin
• Hyperglycaemia
• Increased blood fatty acids
• Increased blood amino acids
• Osmotic diuresis
• Polyuria
• Hypotension
• Hyperkalaemia

Question 28

What are the symptoms of type 1 diabetes Mellitus?

Answer 28

• Increased thirst and urination
• Hunger
• Weight loss
• Fatigue
• Irritability
• Blurred vision

Question 29

What is insulin replacement therapy?

Answer 29

It’s a treatment for diabetes that involves administering insulin to replace the insulin that the body is unable to produce on its own

Question 30

What are the symptoms of type II DM? (6)

Answer 30

• Increased thirst
• Increased hunger
• Frequent urination
• Weight loss
• Fatigue blurred vision
• Headaches

Question 31

What are the treatments for type II DM?

Answer 31

• Sulphonyurea drugs - stimulate insulin secretion
• Biguanide drugs - upregulate receptors on target tissues
• Calorie restriction / weight reduction

Question 32

What is often associated with type II DM?

Answer 32

Obesity

Down regulation of insulin receptors in target tissue + insulin resistance