Endocrinology- Exam 2 (Part 2)- Pancreas (copy)

What are clusters of endocrine cells of the pancreas called?

islets of langerhans

What 4 cells make up the islets of langerhans and what do they each secrete?

-Beta cells (75%), secrete insulin

-Alpha cells (20%), secrete glucagon

-Delta cells (4%), secrete somatostatin

-PP cells (1%)- secrete pancreatic polypeptides

What is the process of insulin synthesis (long-ish card)

- Transcription/Translation of preproinsulin

-N-terminal Signal peptide cleaved, forming proinsulin

-Proinsulin moved to RER and disulfide bridges form

-proinsulin packages into golgi, while also cleaving the connecting peptide--> forming INSULIN

T/F: Insulin is a peptide hormone

True

What does preproinsulin contain?

-N-terminal signal peptide

-A and B chains of insulin

-Connecting peptide (C-peptide)

Where does insulin synthesis take place?

Beta cell of pancreas

Where does insulin and the cleaved connecting protein go after insulin forms?

packaged together into secretory granules

What is a good marker for seeing how responsive Beta-Cells of the pancreas are without looking at insulin (since insulin has a short half-life)?

C-peptide!

Released together with insulin but has a longer half-life

What are the 2 pools that secretory granules of C peptide and insulin are placed into?

-Ready Releasable pool (5%)

-Reserve pool (95%)

how are secretory granules containing insulin and C-peptide released?

exocytosis

Which hormone discussed in lecture can decreased blood glucose levels?

Insulin!

What is the main stimulus for pancreatic Beta cells to release insulin? TQ

Elevated glucose

Explain the process of regulating insulin release (long-ish card)

TQ understand this process

- GLUT2 on beta cell membrane allows blood glucose into the cell via facilitated diffusion

-glucose undergoes glycolysis and increases ATP

- increased ATP causes K+ channels to close, increases charge in the cell

-the membrane depolarizes, there is an influx of calcium and this signals exocytosis of insulin in secretory granules into the venous blood

Insulin has a half life of _____ to ______ minutes and is cleared from the system in _____ -______ minutes.

3; 8; 10; 15

What are the target tissues of insulin? TQ

liver, muscle, adipose tissue

What are the 2nd messenger pathways involved/used in the target tissues of insulin (liver, muscle, adipose tissue)?

PI3K and MAPK

What decisions do the PI3K and MAPK pathways make in the liver, muscle and adipose?

liver-> use it, store it, make fat and cholesterol

muscle-> use it, store it

adipose-> store it (as fat)

Which insulin target tissues utilized GLUT 4 receptors and have high affinity for insulin (meaning insulin must be bound to bring glucose into the cell) ? TQ

skeletal muscle and adipose tissue

Insulin utilizes which type of physiologic mechanism?

What signaling pathways are used? TQ

-Tyrosine kinase mechanism

-PI3K and MAPK

What is the overall action of insulin at the target tissue?

ANABOLIC!- promotes synthesis of carbohydrate, fat and proteins

Where are GLUT2 receptors found? TQ

Liver (hepatocytes) and pancreatic beta cells

T/F: Both GLUT2 and GLUT4 transporters utilize facilitated diffusion

Is GLUT 2 Insulin sensitive?

NO

is GLUT 4 insulin sensitive?

YES

Which is bi-directional: GLUT 2 or GLUT 4?

GLUT 2

Which is translocated to the cell's surface via insulin binding to a tyrosine kinase receptor?

GLUT 4

the liver uses a _______ receptor to bring in glucose to the cell. This glucose is converted into __________ via ____________ and ____________ via ___________. TQ

GLUT2; glycogen; glycogenesis; pyruvate; glycolysis

the muscle uses a _________ receptor to bring glucose into the cell. Glucose is converted to both ___________ via _____________ and ____________ via __________. TQ

GLUT4; glycogen; glycogenesis; pyruvate; glycolysis

Adipose tissue uses a _______ receptor to bring glucose into the cell. Glucose is converted into ______ and __________ to make ______________. TQ

GLUT4; glycerol; fatty acids; triglycerides (lipogenesis)

What is the controller of insulin levels in the blood?

What is the sensor?

liver, pancreas

T/F: decreasing blood glucose causes pancreas to decrease insulin secretion

TRUE

The lack of insulin activates what enzyme, causing the splitting of glycogen into glucose phosphate (glucagon)?

Phosphorylase

Resting muscle uses ___________ kcal/hour.

Moderate exercising muscle uses ___________ kcal/hour.

Hard exercising muscle uses ___________ kcal/hour.

- 5

- 100-150

- 200-300

T/F: trained muscle holds less glycogen due to the high demand of energy the muscle needs.

FALSE: trained muscles hold more glycogen and have a larger storage capacity

What happens when more carbs are ingested than the liver and muscle can use?

insulin promotes fatty acid synthesis, this is then transported to adipose tissue

(LIPOGENESIS)

What hormone does insulin inhibit in adipose tissue and why?

hormone sensitive lipase (HSA) to keep FA in the cell to combine with glycogen to make more TGs

(HSL typically releases FA from adipose to circulation)

what does SWAT and VWAT stand for?

SWAT: subcutaneous white adipose tissue

VWAT: Visceral white adipose tissue

T/F: Adipose tissue growth is strictly through hyperplasia.

FALSE; strictly through hypertrophy

What are the main signs of inflammation in the adipose tissues?

Crown-like structures (CLS)

Which of the following hormones does NOT increase blood glucose levels?

GH

Cortisol

TH

Catecholamines

ADH

ADH