Exam #4: Endocrine Physiology Flashcards Preview

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Flashcards in Exam #4: Endocrine Physiology Deck (30):
1

What are the cell types found in the pancreatic islets?

Alpha
Beta
Delta
Epsilon
PP of F

2

What hormones are secreted by the alpha cells of the pancreatic islets?

glucagon
proglucagon

3

What hormones are secreted by the beta cells of the pancreatic islets?

Insulin
Proinsulin
C-peptide
IAPP
GABA

4

What hormones are secreted by the delta cells of the pancreatic islets?

Somatostatin, negative regulator of insulin secretion

5

What hormones are secreted by the epsilon cells of the pancreatic islets?

Ghrelin

6

What hormones are secreted by the F cells of the pancreatic islets?

Pancreatic polypeptide

7

What are the biosythetic steps of insulin?

1) Insulin gene translated to preproinsulin in ER
2) Preproinsulin is cleaved immediately
3) Proinsulin is packaged into secretory vesicles
4) Conversion of proinsulin to insulin and C-peptide in the secretory vesicles

*Thus, C-peptide and insulin are secreted together. C-peptide is an emerging area of research & a marker of insulin secretion.

8

What is the half-life of insulin?

3-5 min because it circulates in a unbound form, which gives it a short half-life

9

What are the stimulators of insulin? Outline the mechanisms of insulin secretion by these stimulators.

Glucose= most potent stimulator of insulin release
- Glucose moves down its concentration gradient into the pancreatic beta cell; this increase in intracellular glucose leads to an increase in ATP/ ADP ratio
- Increased ATP/ADP ratio leads to closing of a K+ channel
- Beta cell membrane leads to DEPOLARIZATION b/c of the accumulation of K+ (positive charge) on the inside of the cell
- Sensed by a voltage-gated Ca++ channel
- Ca++ rushes in
- Insulin vesicles are exocytosed

Vagal stimulation
- ACh activates muscarininc 3 receptors
- Gq
- PLC
- Intracellular Ca++ increase leads to vesicular docking and insulin release

10

What are the amplifiers of insulin?

Hormones
- Glucagon like peptide (GLP1)*****
- Gastric inhibitory peptide (GIP)
- Cholecystokinin (CKK)
- Gastrin
- Secretin

Catecholamines
- B-adrenergic stimulation i.e. an epinephrine surge

11

What are the inhibitors of insulin?

Hormones
- Somatostatin

Catecholamines
- alpha-adrenergic stimulation
- SNS

12

What are the cellular events that occur following activation of the insulin receptor?

1) Insulin binds to the insulin receptor
2) Activation of large number of intracellular molecules
3) Promotion of GLUT4 transporters insertion into the membrane so glucose can flow down its concentration gradient into the cell

Insulin receptors regulate mitogenic and metabolic processes

13

What tissues utilize glucose transporters for the cellular uptake of glucose?

GLUT4 is the glucose transporter that is regulated by insulin, the other transporters ARE NOT
- Skeletal muscle
- Adipose tissue

14

What are the metabolic consequences of insulin in the liver?

1) Promotion of anabolism
- Glycogen synthesis & storage
- Inhibition of glycogen breakdown
- Increased protein synthesis
- Increased triglyceride synthesis

2) Inhibition of catabolism
- Inhibit glyocogenolysis
- Inhibit ketogenesis (fat to FFA)
- Inhibit gluconeogenesis

*Generally, you're promoting the formation of bigger molecules and the breakdown of bigger molecules into smaller ones

15

What are the metabolic consequences of insulin in the adipose tissue?

Increased triglyceride storage by:
- Promoting FFA uptake
- Promoting esterification of FFA
- Inhibition of lipolysis

16

What are the metabolic consequences of insulin in the skeletal muscle?

1) Increased protein synthesis by increasing amino acid uptake
2) Increased glycogen synthesis
- Increased glucose uptake by GLUT4
- Increased glycogen synthase activity
- Inhibition of glycogen phosphorylase

17

What is glucagon? What are the general effects of glucagon binding to the glucogon receptor?

- Peptide hormone that is produced by the alpha cells of the pancreas & endocrine cells of the gut; has an opposite effect of insulin
- Binds a GPRC that eventually promotes glucose output and ketone body output

Remember, insulin= energy storage, glucagon= energy mobilization

18

What are the regulators of glucagon secretion?

1) Glucose inhibits glucagon secretion--the precise mechanism is unclear
2) Catecholamines and GI hormones promote glucagon release
3) PNS & SNS stimulation can promote glucagaon release
4) Fatty acids suppress glucagon

19

Compare the impact of glucagon & insulin on gluconeogenesis.

Insulin= decreases/ inhibits gluconeogenesis

Glucagon= increases or stimulates gluconeogenesis

20

Compare the impact of glucagon & insulin on glycogenesis/ glycogenolysis.

Insulin= promotes glyocogenesis i.e. formation of glycogen

Glucagon= promotes glycogenolysis i.e.breakdown of glycogen

21

Compare the impact of glucagon & insulin on glycolysis.

Insulin= increases glycolysis

Glucagon= decreases glycolysis

22

Compare the impact of glucagon & insulin on ketogenesis.

Low insulin & high glucagon= formation of ketone bodies i.e. ketogenesis

23

How do insulin and glucagon effect blood glucose levels?

Glucagon= raise

Insulin= lower

24

What are GLPs?

Glucagon-like peptides

25

What is the function of GLP1?

- Secreted in response to glucose, lipids, and PNS
- Promotes BOTH insulin and somatostatin secretion
- Protects and promotes growth of B-cells

26

What is dipeptidyl peptidase 4 (DPP-4)?

Enzyme that degrades GLP1

27

What is IAPP & what is the function of IAPP?

- Islet amyloid polypeptide that is produced by B-cells
- Secreted by stimuli that increase insulin secretion
- Decreases glucagon secretion & inhibits GI motility/ gastric emptying

28

What is Pancreatic Polypeptide, & what is the function of Pancreatic Polypeptide?

- Produced and secreted by F cells
- Neuronal control
- Regulates EXOCRINE function of the GI tract i.e. gallbladder contraction, gastric acid secretion, and GI motility

29

What is Somatostatin & what is the function of Somatostatin?

- Produced by delta cells
- Inhibits insulin secretion in a paracrine fashion through activation of SSTR-5

30

What is Ghrelin & what is the function of Ghrelin?

- Produced by epsilon cells
- Induces gastric emptying, promotes acid secretion, and increases appetite

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