Endocrine Pancreas

Question 1

What are the endocrine cells of the pancreas arranged into?

Answer 1

Islets of Langerhans (clusters)

Question 2

What type of cells exist in the islets of Langerhans?

Answer 2

alpha cells
beta cells
delta cells
F cells

Question 3

What do alpha cells release in the endocrine pancreas?

Answer 3

Glucagon

Question 4

What do beta cells release in the endocrine pancreas?

Answer 4

Insulin and C peptide

Question 5

What is C peptide used for?

Answer 5

To measure function of beta cells and of endogenous insulin secretion

Question 6

What do delta cells release in the endocrine pancreas?

Answer 6

Somatostatin

Question 7

What do F cells release in the endocrine pancreas?

Answer 7

Pancreatic polypeptide

Question 8

Where are the alpha cells located in the islets?

Answer 8

Periphery

Question 9

Where are the beta cells located in the islets?

Answer 9

Central

Question 10

Where are delta cells located in the islets?

Answer 10

Interspersed between alpha and beta cells

Question 11

What is the signal the F cells send?

Answer 11

Satiety (feeling full)

Question 12

What stimuli causes beta cells to release insulin?

Answer 12

GLUCOSE ingestion

Question 13

What is the majority cell in the endocrine pancreas (60%)?

Answer 13

Beta cells

Question 14

How do cells within the islet communicate with each other?

Answer 14

Gap junctions based on ion concentration changes

Question 15

Describe the blood flow to the islets of Langerhans in the pancreas

Answer 15

• Blood flows into the central region first, contacting the beta cells
• Then the venous blood flows from the central region to the peripheral region, contacting the alpha and delta cells
• This brings insulin (from beta cells) to the alpha and delta cells which inhibits the alpha cells from releasing its product (glucagon)

Question 16

What is the order of how insulin is made?

Answer 16

• Preproinsuliln
• Proinsulin - packaged into vesicles and cleaved by proteases
• Insulin and C peptide

Question 17

What is the function of the endocrine pancreas cells?

Answer 17

Regulate lipid, carb, and AA metabolism

Question 18

What receptor is used to bring glucose into a beta cell?

Answer 18

GLUT - 2

Question 19

What are the steps to insulin and C peptide release from a beta cell?

Answer 19

1. Glucose enters cell via GLUT-2
2. Glucose is phosphorylated/oxidized to generate ATP
3. Rising ATP levels CLOSES K+ channel so K+ remains in the cell
4. This moves the cell towards more depolarization and opens Ca++ channels
5. Ca++ allows the vesicles containing insulin and C peptide granules to be released out of the cell

Question 20

What is the name of the receptor that closes the ATP-dependent K+ channels and what does it ultimately result in?

Answer 20

Sulfonylurea receptor = INCREASES insulin secretion

Question 21

Describe the insulin release based on time after eating

Answer 21

• Initial spike of insulin release within MINUTES after eating
• Then it returns to normal but slowly INCREASES about an hour later

Question 22

Describe the overall summary of Type 2 diabetes

Answer 22

• Glucose levels are normal or elevated
• Pancreas beta cells secrete MORE insulin
• Peripheral tissues (adipose, skeletal muscle, liver) do NOT respond!
  “insulin resistance”

Question 23

When does insulin resistance begin to occur with type 2 diabetes?

Answer 23

Very early in disease progression

Question 24

What receptor is used to bring glucose into peripheral tissues?

Answer 24

GLUT-4

Question 25

Describe how glucose is supposed to be brought into peripheral tissues (adipose, skeletal muscle, liver)?

Answer 25

- Insulin binds to receptor - MAP kinases mediate downstream pathways - - Translocation of vesicle containing GLUT-4 sent to plasma membrane = Glucose enters cell via facilitated diffusion

Question 26

What are some stimuli that activate insulin secretion?

Answer 26

``` Increased glucose Glucagon Ach CCK Cortisol K+ Sulfonylruea drugs ```

Question 27

What are some stimuli that inhibit insulin secretion?

Answer 27

``` Somatostatin Decreased glucose Fasting Exercise NE ```

Question 28

What does insulin promote peripheral tissues to do?

Answer 28

Uptake/store glucose

Question 29

Insulin also promotes K+ _____, which causes _____

Answer 29

Uptake | This causes decreased K+ levels in the blood

Question 30

What can stimulate glucose uptake independent of insulin?

Answer 30

Muscle contraction

Question 31

What is the role of glucagon?

Answer 31

To INCREASE glucose levels

Question 32

What does glucagon promote peripheral tissues to do?

Answer 32

Glucose formation

Question 33

What are the major activators and inhibitors of glucagon release?

Answer 33

``` (+) = decreased glucose levels (-) = insulin ```

Question 34

Which type of diabetes mellitus has more of a genetic component that predisposes them to the condition?

Answer 34

Type 2

Question 35

What are some factors that lead to the development of Type 2 DM?

Answer 35

``` Excessive caloric intake Sedentary behavior Genetic component Ethnicity - african american Adipose tissue dysfunction and chronic inflammation ```

Question 36

Steps to insulin resistance and Type 2 DM

Answer 36

1. Insulin release 2. Hyperinsulinemia - normal glucose levels but takes more insulin to get them there 3. Postprandial hyperglycemia 4. Disrupted response to oral glucose tolerance test 5. Chronic elevated insulin levels 6. Mild to moderate elevated glucose levels 7. Hyperglycemia

Question 37

How long can it take to develop Type 2 DM?

Answer 37

5-30 years

Question 38

Type 1 diabetes mellitus

Answer 38

Autoimmune destruction of beta cells = NO insulin or C peptide release!

Question 39

Signs of Type 1 diabetes mellitus

Answer 39

``` Childhood onset Hyperglycemia Diabetic ketoacidosis Hyperkalemia Polydipsia (thirst) ```