Physiology Ch. 78: Insulin And Glucagon

Front 1

Function of the islet of langerhans

Back 1

secrete insulin and glucagon directly into the blood

Front 2

delta cell

Back 2

secretes somatostatin

Front 3

alpha cell

Back 3

secretes glucagon

Front 4

b cell

Back 4

insulin and amylin

Front 5

Insulin allows excess carbs to be stored as what, where?

Back 5

Glycogen in the liver and muscle tissue. After glycogen stores are full, the carbs are converted to fats and stored in adipose tissue.

Front 6

How does insulin affect proteins

Back 6

Inhibits the breakdown of proteins and increases the uptake and conversion of amino acids to protein

Front 7

Insulin is first formed where? As what molecule?

Back 7

RER
Insulin Preprohormone

Front 8

Does proinsulin have hormonal activity

Back 8

NO

Front 9

Is insulin carried by binding proteins through the blood?
What happens to insulin that does not bind to its target receptor?

Back 9

NO
It is degraded by insulinase, mostly in the liver

Front 10

Insulin receptor

Back 10

Consists of 4 subunits:
2 alpha that lie entirely outside the cell
2 beta that penetrate through the membrane

Front 11

What portion of the receptor does insulin bind?
What becomes autophosphorylated? What does this activate?

Back 11

Alpha
Beta
Activates Tyrosine Kinase, which in turn causes phosphorylation of multiple other intracellular enzymes including IRS

Front 12

Insulin's affects are most prominently not seen where?

Back 12

Neurons of the brain

Front 13

The main physiological affect of insulin is to increase glucose transport how?

Back 13

Increases the translocation of intracellular vesicles to the membrane that contain glucose transport binding proteins.

Front 14

How does insulin affect the transport of K and phosphate ions

Back 14

Causes the cell membrane to become more permeable, increasing the uptake and causing a decrease in their extracellular concentration

Front 15

During most of the day, what is the main form of energy? Why?

Back 15

Fatty acids
Because normal resting muscle is impermeable to glucose, except when the muscle fiber is stimulated by insulin.

Front 16

Under what conditions do muscle fibers not need insulin for glucose uptake?

Back 16

During Exercise

Front 17

When does the muscle use insulin

Back 17

After a meal

Front 18

Mechanism by which insulin causes glycogen storage in the liver

Back 18

1. Inactivates liver phosphorylase:
Causes liver to split glycogen into glucose
2. Increases the activity of glucokinase which increases the uptake of glucose into the cell.
3. Increases the activity of glycogen synthase

Front 19

Lack of insulin activates what enzyme that begins gluconeogenesis

Back 19

Liver phosphorylase breaks down glycogen into glucose phosphate which is then broken don into glucose by glucose phosphatase

Front 20

The brain uses mainly what for energy

Back 20

Glucose

Front 21

The transport of glucose into adipose tissue provides a substrate for?

Back 21

Glycerol portion of triglycerides

Front 22

Is insulin a fat sparer? How?

Back 22

Yes; it utilizes glucose uptake which automatically decreases fat utilization

Front 23

How does insulin increase fatty acid synthesis

Back 23

1. An increase of glucose uptake into cells, increases the amount of glycogen synthesis. Once glycogen synthesis is overloaded, the glucose is made into pyruvate, which is converted to Acetyl Co-A.
2. Excess citrate and isocitrate activate acetyl-CoA carboxylase to form malonyl-CoA.
3. Activates lipoprotein lipase, which spilts TG's into fatty acids for transfer into adipose cells.

Front 24

In the absence of insulin, what is the most important affect for lipolysis of fat

Back 24

Activation of hormone-sensitive lipase

Front 25

In the absence of insulin, and in the presence of excess fatty acids, what happens to the carnitine transport system?

Back 25

Increases its activity, thus beta oxidation of fatty acids within the mitochondria increases, releasing large amounts of acetyl-coa, which form ketone bodies

Front 26

How does insulin decrease gluconeogenesis?

Back 26

Decreases the activity of the enzymes that promote it, mostly by decreasing their substrates. Such as amino acids.

Front 27

How does insulin lack affect protein storage?

Back 27

Leads to increased protein catabolism and increased amino acid concentration.This in turn leads to amino acid breakdown and the formation of excess urea, which is excreted in the urine.
Protein wasting leads to increased muscle wkns

Front 28

How does insulin and growth hormone affect growth?

Back 28

When given together they act synergistically to increase growth

Front 29

Rate limiting enzyme for glucose metabolism in the pancreatic B-cell and insulin secretion

Back 29

Glucokinase
Glucose to Glucose-6-phosphate

Front 30

Glucose transporter on the pancreatic B cell

Back 30

GLUT2

Front 31

Insulin is released into the bloodstream by

Back 31

exocytosis

Front 32

How does glucose metabolism within the B cell affect insulin secretion

Back 32

Increased metabolism increases ATP and inactivates the ATP-dependent Kchannel, that causes depolarization of the cell, and opening voltage gated Ca channels, which cause an influx of Ca into the cell. This stimulates the fusion of insulin vesicles with the membrane

Front 33

Major hormones that inhibit insulin secretion

Back 33

somatostatin, norepi, and leptin

Front 34

How does amino acid concentration affect insulin secretion? What happens when glucose is also present?

Back 34

Increased amino acid concentration increases insulin secretion only SLIGHTLY.
Glucose-induced secretion of insulin may be doubled in the presence of amino acids. Thus, amino acids strongly potentiate the glucose stimulus for insulin secretion. This allows for protein synthesis.

Front 35

Most potent amino acids for insulin secretion

Back 35

Arginine and Lysine

Front 36

What is the stimulus for fat utilization in insulin lack

Back 36

Decreased blood glucose activates gluconeogenesis

Front 37

Major hormones secreted in response to hypoglycemia

Back 37

Glucagon
GH
Cortisol
Epinephrine

Front 38

The hyperglycemic hormone

Back 38

Glucagon

Front 39

Most dramatic effect of glucagon

Back 39

Ability to cause glyocogenolysis in the liver

Front 40

Glycogenolysis mechanism

Back 40

Glucagon activates adenylyl cyclase, which causes the formation of cAMP. This in turn activates protein kinase, which activates phosphorylase B kinase. This then works to activate phosphorylase B into phosphorylase A. This promotes the degradation of glycogen into glucose-1-phosphate, which is dephosphorylated into glucose.

Front 41

How does Glucagon affect gluconeogenesis?

Back 41

Increases the uptake of amino acids into the liver and the conversion of them to glucose via gluconeogenesis.

Front 42

When glucagon is maximally elevated, what is its effect on hormone sensitive adipose cell lipase?

Back 42

Increases it, causing an increase in fatty acid concentration. Glucagon also inhibits the storage of TG's in the liver.

Front 43

Most potent factor that controls blood glucose

Back 43

Blood Glucose levels

Front 44

In what instance is both insulin and glucagon stimulated at the same time?

Back 44

Increased blood amino acids

Front 45

What factors increase somatostatin secretion?

Back 45

Increase Blood glucose
Increased AA's
Increased FA's
Increased GI hormones

Front 46

How does somatostatin work to depress insulin and glucagon production?

Back 46

It has autocrine function
I works locally within the islets of langerhans

Front 47

Principal Function of somatostatin

Back 47

Extends the time over which food nutrients are digested and assimilated into the blood. Prevents rapid exhaustion of food and therefore making it available over a longer period of time

Front 48

Why is it important to maintain a constant blood glucose concentration?

Back 48

Glucose is the only nutrient that normally can be used by the brain, retina, and germinal epithelium of the gonads.

Front 49

In pts with sever liver disease, how is blood glucose affected?

Back 49

It is impossible to correctly store glucose as glycogen during excess energy states, and thus, impossible for the glycogen to be broken down into glucose during hypoglycemic states.
The blood sugar is highly variable

Front 50

Syndrome associated with marked increases in ovarian androgen production and insulin resistance

Back 50

Polycystic ovary syndrome