Endocrine 04 - Regulation Of Metabolic Homeostasis: Insulin/glucagon

Front 1

What is the major function of insulin?

Back 1

Store substrates for fuel.

Front 2

What is the major function of glucagon?

Back 2

Mobilize fuel substrates for the body to use.

Front 3

Where is glucagon synthesized?

Back 3

Pancreas (α-cells)

Front 4

Where is insulin synthesized?

Back 4

Pancreas (β-cells)

Front 5

Where is somatostatin synthesized?

Back 5

Pancreas (δ-cells)

Front 6

Where is proinsulin converted to its active form?

Back 6

Within the secretory granules of the pancreatic β-cells.

Front 7

What glucose transporter is found on the surface of pancreatic β-cells?

Back 7

GLUT2.

Front 8

What is the "pancreatic glucose sensor" and why?

Back 8

Glucokinase because of its high Km for glucose. As more glucose enters the pancreas, the more insulin is released.

Front 9

What is the result of blocking K+ channels in β-cells?

Back 9

Blocking K+ channels results in a greater release of insulin, induced by sulfonylurea drugs in Type II diabetics.
Sulfonylurea drugs will also increase intracellcular Ca which increases vesicle formation and release.

Front 10

Describe the pattern of insulin secretion over time.

Back 10

An injection of glucose reveals a sharp initial spike followed by a sharp drop of plasma insulin. A slower second phase ensues and plasma insulin begins to rise steadily.

Front 11

What is the major function of insulin?

Back 11

Store substrates for fuel.

Front 12

What is the major function of glucagon?

Back 12

Mobilize fuel substrates for the body to use.

Front 13

Where is glucagon synthesized?

Back 13

Pancreas (α-cells)

Front 14

Where is insulin synthesized?

Back 14

Pancreas (β-cells)

Front 15

Where is somatostatin synthesized?

Back 15

Pancreas (δ-cells)

Front 16

Where is proinsulin converted to its active form?

Back 16

Within the secretory granules of the pancreatic β-cells.

Front 17

What glucose transporter is found on the surface of pancreatic β-cells?

Back 17

GLUT2.

Front 18

What is the "pancreatic glucose sensor" and why?

Back 18

Glucokinase because of its high Km for glucose. As more glucose enters the pancreas, the more insulin is released.

Front 19

What is the result of blocking K+ channels in β-cells?

Back 19

Blocking K+ channels results in a greater release of insulin, induced by sulfonylurea drugs in Type II diabetics.

Front 20

Describe the pattern of insulin secretion over time.

Back 20

Biphasic. An injection of glucose reveals a sharp initial spike followed by a sharp drop of plasma insulin. A slower second phase ensues and plasma insulin begins to rise steadily.

Front 21

In what situation would a patient have zero insulin in the circulation?

Back 21

In Type I diabetes only. In every other situation, there is a basal release of insulin to the circulation.

Front 22

What drugs works in opposition to sulfonylurea drugs?

Back 22

Diazoxide.

Front 23

What key event occurs following insulin binding to its membrane surface receptor?

Back 23

The insulin-receptor complex is endocytosed, making the receptor unavailable for future binding.

Front 24

What 2 events occur within seconds of insulin secretion?

Back 24

1) Insulin binds to its receptor
2) The receptor activates its secondary messengers.

Front 25

What events occur within minutes of insulin secretion?

Back 25

1) Gene transcription
2) Increased ion transport
3) Ligand-mediated receptor internalization
4) Enzyme activity is modulated

Front 26

What events occur within hours of insulin secretion?

Back 26

1) Protein, lipid, and nucleic acid synthesis
2) Complete downregulation of the receptor
3) Cell growth

Front 27

What are the anabolic effects of insulin on the liver?

Back 27

1) Promotes glycogenesis (glycogen storage)
2) Promotes synthesis of TAGs, cholesterol, and VLDL
3) Promote protein synthesis
4) Promote glycolysis (use glucose in circulation)
*Excess glucose - use glucose in circulation and store the leftover.

Front 28

What are the 3 anti-catabolic effects of insulin on the liver?

Back 28

1) Inhibits glycogenolysis (do not mobilize glucose)
2) Inhibits ketogenesis
3) Inhibits gluconeogenesis

Front 29

What effect does insulin have on glycogen synthesis?

Back 29

Increases the synthesis of glycogen by increasing glucose uptake, promoting glycogen synthase, and inhibiting glycogen phosphorylase.

Front 30

What effect does insulin have on protein synthesis?

Back 30

Increases protein synthesis by increasing amino acid transport and stimulating ribosomes to synthesize proteins.

Front 31

What effect does insulin have on lipids?

Back 31

Promote triglyceride storage by activating lipoprotein lipase to release FFA's for storage as TAG, inhibits lipolysis.

Front 32

Why is it especially dangerous for insulin levels to be low in plasma?

Back 32

Because very high levels of insulin are required to uptake normal levels of glucose.

Front 33

*What polypeptides are synthesized from transcription of the glucagon gene?

Back 33

1) Glucagon
2) GLP-1 and GLP-2

Front 34

What do GLP-1 and GLP-2 do?

Back 34

They activate insulin secretion, opposing the action of glucagon.

Front 35

What effect does stress have on plasma glucose levels?

Back 35

Stimulate glucagon and inhibit insulin, so glucose will be released into the circulation.

Front 36

What is the relationship between levels of glucose, insulin, and glucagon?

Back 36

An injection of glucose results in increases of insulin, and a decrease in glucagon.

Front 37

*How would the injection of a gluconeogenic amino acid (arginine) affect glucose, insulin, and glucagon levels?

Back 37

Infusion of arginine would cause a very small increase of glucose, a sharp increase of insulin, and interestingly, a sharp increase in glucagon.

Front 38

What substrates are produced when glucagon binds to receptors on the liver?

Back 38

Glucose and ketone bodies.