1a Glucose Homeostasis

Question 1

What is significantly impaired when glucose concentration falls below normal levels?

Answer 1

Cerebral function

Question 2

What is glucose particularly important for?

Answer 2

The functioning of the central nervous system

Question 3

What is hypoglycemia?

Answer 3

Blood glucose concentration levels fall below a normal levels

Question 4

What can happen is blood glucose Concentration falls below 2mmol/L

Answer 4

Unconsciousness, coma and ultimately death

Question 5

What does persistent hyperglycemia result in?

Answer 5

Diabetes mellitus

Question 6

What hormones act against hypoglycemia?

Answer 6

Glucagon
Cortisol
Growth hormone
Catecholamines

Question 7

What is the most prevalent form of diabetes?

Answer 7

Type 2 diabetes mellitus

Question 8

What are the three types of diabetes

Answer 8

Type 1 DM
Type 2 DM
maturity onset diabetes of the young

Question 9

What is meant by a retroperitoneal structure?

Answer 9

Has a peritoneum on the anterior side only

Question 10

What are the small clumps of cells in the pancreas called?

Answer 10

Islets of Langerhans

Question 11

What are exocrine acinar cells?

Answer 11

Cells that generate exocrine secretions

Question 12

What are the three types of islet cells?

Answer 12

Alpha, beta and delta cells

Question 13

What are the alpha cells involved with?

Answer 13

Glucagon secretion

Question 14

What are the beta cells in the islets of langerhans involved with?

Answer 14

Insulin secretion

Question 15

What are the delta cells in the islet of langerhans involved with?

Answer 15

Somatostatin secretion

Question 16

What effect does somatostatin have on insulin and gluacagon?

Answer 16

Somatostatin inhibits both in a negative feedback loop to keep them in balance

Question 17

How does glucagon and somatostatin affect the release of insulin from beta cells when there is a rise in blood glucose?

Answer 17

• Glucagon stimulates release of insulin
• Somatostatin inhibits the release of insulin

Question 18

How do the GI hormones and amino acids affect the secretion of insulin from the beta cells when there is a rise in blood glucose?

Answer 18

Both increase secretion of insulin

Question 19

How do SNS and PNS activity affect the secretion of insulin when there is a rise in blood glucose?

Answer 19

SNS - inhibits secretion of insulin via alpha cells
PNS activity stimulates the release of insulin

Question 20

What are gap junctions?

Answer 20

They allow small molecules to pass directly between cells

Question 21

What are tight junctions?

Answer 21

Create small intercellular spaces

Question 22

What type of communication is found between the islet cells?

Answer 22

Paracrine communication

Question 23

What does insulin do?

Answer 23

Stimulates growth and development and reduces blood glucose

Question 24

What affect does insulin secreted from the beta cells have?

Answer 24

Increased:
- Glycolysis
- Glycogenesis
- Glucose transport into cells via GLUT 4

Question 25

Where is GLUT 4 predominantly expressed?

Answer 25

Adipocytes and skeletal muscle

Question 26

When blood glucose is high, what is released?

Answer 26

Insulin from the beta cells as well as some glucagon from the alpha cells to ensure that hypoglycaemia doesn’t occur

Question 27

Aside from glucose effects, what else does insulin do?

Answer 27

Increase amino acid transport, protein synthesis and lipogenesis Decrease in lipolysis

Question 28

What is released when blood glucose levels are lowered?

Answer 28

Alpha cells release glucagon

Question 29

What affect does glucagon have?

Answer 29

INCREASED: - gluconeogenesis - lipolysis - blood glucose - amino acid transport to the liver - hepatic glycogenolysis

Question 30

Is GLUT 2 insulin sensitive?

Answer 30

No

Question 31

What is the main glucose sensor?

Answer 31

Glucokinase (hexokinase as IV)

Question 32

What is GLUT 2’s affinity for glucose, and what does this mean?

Answer 32

Low affinity for glucose, so glucose is able to be moved into the liver cell and beta cell in proportion to the plasma level of glucose

Question 33

Does glucose 6 phosphate inhibit glucokinase?

Answer 33

No

Question 34

Why do glucose 6 phosphate levels give a good indication of glucose levels as well?

Answer 34

Glucose to glucose 6 phosphate is a continual conversion by glucokinase therefore the amount of glucose present is equal to glucose 6 phosphate

Question 35

Describe the process by which insulin is released from the beta cells after blood glucose increases?

Answer 35

1. **Glucose transported into beta cell** by **GLUT-2** 2. Glucose in the cell undergoes glycolysis by **Glucokinase** (hexokinase IV) to **produce ATP** (Rate-Limiting Step) 3. **ATP inhibits the K+ efflux pump** so K+ remains intracellularly and builds up in the cell, this relative increase leads to **membrane depolarisation** 4. This **opens Ca2+ voltage gated channels** leading to **Ca2+ influx** which promotes **secretion of stored insulin** in beta cell

Question 36

What is meant by a graded response of insulin production?

Answer 36

Insulin isn’t released in an all or nothing manner, continually released when needed and the amount released changes over time

Question 37

What is pro insulin cleaved into?

Answer 37

Pro insulin and C-peptide

Question 38

What happens to C peptide levels after a big meal?

Answer 38

Increase

Question 39

What happen to someone’s C peptide levels when a person with type 1 diabetes eats a meal?

Answer 39

They are low - this is because C peptide levels are only a measure of endogenous insulin, and doesn’t include the insulin which they have injected following the meal

Question 40

Why is measuring endogenous C-peptide a good indicator for insulin?

Answer 40

C peptide is more stable than insulin

Question 41

What is the difference between oral and intravenous glucose in terms of plasma insulin production? And what is this effect called?

Answer 41

Oral is significantly higher - increatin effect

Question 42

Transcription of what gene produced Glucagon like peptide 1?

Answer 42

Pro-glucagon gene

Question 43

Where is glucagon like peptide found?

Answer 43

In the gut

Question 44

What is the effect of glucagon like peptide 1?

Answer 44

Stimulated insulin and suppresses glucagon

Question 45

What effect does glucagon like peptide1 do to us?

Answer 45

Increases feeling of fullness by delaying gastric emptying

Question 46

Why does GLP1 have a short half life?

Answer 46

Rapidly degraded by enzymes dipeptidyl peptidase 4

Question 47

What is GLP1 used in the treatment of?

Answer 47

Diabetes mellitus

Question 48

What is meant by the first phase insulin release?

Answer 48

This is following a meal, when a diabetics insulin levels do increase slightly, but much less than a healthy individuals, and stay elevated

Question 49

How does the insulin receptor work?

Answer 49

1. Insulin binds to alpha subunit 2. Causes a confirmation change in the tyrosine kinase domain of the beta sun unit 3. This causes the movement of GLUT 4 from intracellular space to cell membrane so glucose can be absorbed

Question 50

What part of the insulin receptor does insulin initially bind to?

Answer 50

Extracellular domain - alpha subunit

Question 51

What percentage of the pancreas gland is involved in exocrine secretions?

Answer 51

98%

Question 52

Where may you find insulin receptors?

Answer 52

Liver, muscle and fat

Question 53

What is the incretin effect?

Answer 53

When the production of plasma insulin is significantly larger and higher following giving oral glucose to patients