Endocrine Pancreas II Flashcards Preview

Module 6: Repro/Endocrine > Endocrine Pancreas II > Flashcards

Flashcards in Endocrine Pancreas II Deck (19):

What are the effects on:

By Insulin and Glucagon?

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How is glucose utilized during strenuous exercise?

Utilization of glucose by muscle is matched by an increase in hepatic glucose production, mediated in large part by glucagon

--> prevents hypoglycemia and provides another adjustment vital to survival  in "fight or flight" situations


How is glucose utilized during serious injury or shock?

- A prompt rise in glucagon occurs together with a relatively slow insulin level, bringing about "stress hyperglycemia"

--> maximizes glucose delivery to an under-perfused brain



What types of cells are in the Islet of Langerhans? What do they secrete?

Alpha = Glucagon

Beta = Insulin

Delta = Somatostatin (SRIF)


How does somatostatin (released by delta cells) affect other cells in the islet?

SRIF coordinates the secretion of both insulin (beta cells) and glucagon (alpha cells)
- it can inhibit release of either hormone

--> ALL actions of SRIF are inhibitory


What is the process of insulin biosynthesis?

1. Formation of insulin mRNA

2. Ribosomal translation: synthesis into proinsulin

3. Transfer of proinsulin to the golgi complex

4. Packing of proinsulin to golgi complex

5. Conversion of proinsuiln into insulin (posttranslational modification)

6. Formation of zinc-insulin crystals

7. Translocation of granules to beta cell membrane

8. Fusion of granul and cell membrane

9. Liberation of granule (exocytosis)


What conditions are associated with insulin resistance?

--> Decreased insulin binding occurs in:
Mature-onset Diabetes
Growth Hormone excess
Glucocorticoid excess
Lipoatrophic diabetes


What conditions are associated with Insulin hypersensitivity?

--> Increased insulin binding occurs in:
Trained athletes
Glucocorticoid deficiency


How does insulin regulate glucose uptake by cells?

Insulin activates a series of phosphorylations and dephosphorylations that result in increased expression of GLUT 4 transporters on the surface of the cell.

- After binding, insulin and its receptor are usually internalized, constituting an "off switch" for insulin activation

- Majority of internalized hormone undergoes enzymatic degredation in the lysosomes


What are the actions of insulin on the liver?

- Stimulate glucose intake and trapping of glucose via phosphorylation by glucokinase

- Promotes storage of glucose as glycogen by activating glucogen synthase

- Reduces glucose output by inhibiting gluconeogenesis

- Reduces glucose output by inhibiting glycogenolysis through decreasing glycogen phophorylase activity

- Reduces formation of ketone bodies by decreasing beta-oxidationg of FAs


What are the actions of insulin on muscle?

- Stimulates glucose and AA uptake

- Stimulates gluocse storage as glycogen


What are the actions of insulin on adipose tissue?

- Stimulate glucose and AA uptake

- Increase the formation of alpha-glycerophosphate for FA esterification and triglyceride storage


How does insulin promote storage of FAs?

- Accelerates uptake and storage of lipid in adipocytes by stimulating lipoprotein lipase (which converts triglycerides into free fatty acids which are able to enter adipocytes)

- Facilitates glucose uptake into adipocytes (becoming a 3C backbone for TG formation

- Enhances liver FA synthesis and TG release

- Dramatically inhibits hormonally sensitive lipases in adipocytes, further reducing blood levels of free FAs

- Inhibits conversion of FA to ketoacids in hepatocytes


What stimulates insulin release?

- Glucose

- AA

- Glucagon

- Acetylcholine

- Acetylcholine

- GI hormones (i.e. Glucagon-like peptide-I)

- B2 adrenergic receptors - Epinephrine


What inhibits insulin release?

- Somatostatin

- a2 adrenergic receptor


What is the mechanism of B-cell insulin release when activated by glucose?

Glucose metabolism generates ATP

- ATP closes K+ channels resulting in depolarization, leading to Ca2+ channel opening

- Ca2+ mediates insulin release


What tissues does insulin NOT regulate glucose uptake?


- Peripheral neurons (including retina)

- Renal medullary cells

- Cells lining blood vessels

- Liver cells (though it does regulate glucose metabolism in the liver)


What hormones counter insulin?


Cortisol (works much slower than glucagon)

Epi & NE

Growth Hormone