Endocrine pancrease - Insulin

Question 1

Describe absorptive and post absorptive states

Answer 1

Absorptive state
- State just after eating where nutrients are being absorbed and excess stored
Post absorptive state

Question 2

Describe the obligatory glucose utiliser

Answer 2

• The brain can only use glucose as a means of energy, (except in extreme cases of starvation ketones broke down)
• Even if no carbohydrates are gained by the body we must maintain BG level

Question 3

How is blood glucose maintained during post in the post absorptive state?

Answer 3

• BG is maintained by synthesizing glucose from glycogen (Glycogenolyisis)
• BG is also maintained from synthesizing glucose from amino acids (Gluconeogensis)

Question 4

What are the normal ranges of glucose

Answer 4

• Normal 4.3-6.3

[BG] < 3 = Hypoglycemia

Question 5

What portion of the pancreases acts as an endocrine gland?

Answer 5

• 1% of the pancrease acts as an endocrine gland

- 99% of the pancreas acts as a Exocrine gland

Question 6

Describe the functions of the islets of langerhan cells?
Alpha - 
Beta - 
Delta - 
F -

Answer 6

Alpha cells - Glucagon
Beta cells - Insulin
Delta cells - Somatostatin
F cells - Pancreatic polypeptide

Question 7

Describe the effects of insulin and when this dominates?

Answer 7

Insulin dominates during the absorptive fed state

• Glucose oxidation
• Glycogen synthesis
• Fat synthesis
• Protein synthesis

Question 8

Describe the effects of glucagon and when it dominates?

Answer 8

Glucagon

• Glycogenlysis (Breakdown of glycgoen)
• Gluconegensis (Build of glucose from amino acids etc)
• Ketogenesis (Breakdown of ketones to supply the brain)

Question 9

Describe the production of insulin what it stimulates?

Answer 9

Insulin is a peptide hormone synthesised in the ribosome as preproinsluin

• It is converted to proinsulin in the endoplasmic reticulum
• Proinsulin is packeged into secretory granules within the golgi apparatus and converted to insulin with C-peptides
• Insulin is released when B cells are activated

Question 10

What triggers insulin secretion?

Answer 10

• Blood glucose concentration (Main factor)
• ## Uptake of glucose and amino acids aswell

Question 11

How is glucose stored?

Answer 11

• Glucogen in Liver and muscle

- Triglycerides in liver and adipose tissue

Question 12

Describe the mechanism of insulin release

Answer 12

• B cells have a specific K+ ion channel that is sensitive to ATP
• When glucose is in abundance it enters the cell through GLUT transporter and metabolism increases
• This causes ATP production closing the K channels
• This causes cell depolarisation and Ca channels open and trigger insluin exocytosis into circulation

Question 13

Describe B cells when blood glucose is low

Answer 13

• Glucose low less glucose is entering the cells causing less ATP metabolism
• This causes the K ions to stay open and the cell stays hyperpolarised
• This means Ca channels remain closed and no insulin is released

Question 14

Describe the receptors insulin (peptide) binds too?

Answer 14

Binds to tyrosine kinase receptors (Slow effect)

- Only on insulin sensitive tissue Muscle and adipose tissue

Question 15

What does insulin stimulate when binding to tyrosine kinase receptors?

Answer 15

• Stimulates GLUT 4 transporters to come to the surface which normally reside in the cytoplasm
• These GLUT 4 transporters allow insulin to enter the cell

Question 16

Describe what happens when the insulin stimulation stops?

Answer 16

GLUT 4 transporters move back into the cytoplasm and glucose is not able to enter the cell

Question 17

Describe the insulin sensitive tissues?

Answer 17

Muscle and adipose tissue

Question 18

Describe the GLUT 1 transporter

Answer 18

Basal glucose uptake

- Brain, kidneys and red blood cells

Question 19

Describe the GLUT 2 transporter

Answer 19

B cells of the pancreas and the Liver

Question 20

Describe the effect of insluin on the liver?

Answer 20

Insulin triggers hexokinase within the cell, this lowers glucose with in cell

Question 21

Describe the effects of hexokinase within the liver

Answer 21

Hexokinase lowers intracellular glucose, this creates a gradient favouring movement of glucose into the cell
- Enters through the GLUT 2 transporter

Question 22

Describe the anabolic actions of insulin

Answer 22

• Stimulates glycogen synthesis within the muscle and adipose tissue
• Stimulates glycogen synthase and inhibits glycogen phosphorylase
• Increased amino acid uptake in muscle
• Increases protein synthesis and inhibits proteolysis
• Increases triacylglycerol synthesis in adipocytes and liver
• Inhibits enzymes of gluconeogensis in the liver
• Stimulates the uptake of K ion entry into cells

Question 23

Describe the permissive effects of insulin

Answer 23

Has a permissibe effect on growth hormone

Question 24

Describe the stimuli which increases Insulin production

Answer 24

• Increased Blood glucose
• CCK, GLP-1 , GIP
• Glucagon (Balances
• Gastrin, CCK, GLP-1, GIP
• Vagal nerve activity

Question 25

Describe IV glucose release as opposed to oral glucose

Answer 25

• Oral glucose triggers the release of major GI hormones as-well as insulin direct effects
• IV glucose - Only triggers insulin release by direct effect on B cells
• Oral glucose - Direct effect on B cells and vagal stimulation of B cells plus incretin effects