The Endocrine Pancreas- insulin, glucagon and somatostatin

Question 1

When insulin dominates over glucagon, are we in an anabolic or catabolic state?

Answer 1

Anabolic

Question 2

Which type of hormone is insulin?

Answer 2

Peptide hormone

Question 3

Which cells produce insulin?

Answer 3

Pancreatic beta cells

Question 4

Insulin is synthesised as a preprohormone known as preproinsulin which is then converted into proinsulin in the ER.
What happens to proinsulin next?

Answer 4

Packaged as granules into secretory vesicles.
Within the granules, proinsulin is cleaved to form insulin and C-peptide.

Question 5

Instead of measuring insulin levels in a diabetic patient, what would you measure?

Answer 5

C-peptide levels

-> patient could be injecting insulin so measuring this instead indicates endogenous pancreatic beta cell function

Question 6

An increase in BG levels stimulates the release of insulin. What else can trigger the release of insulin?

Answer 6

Increase in amino acids

Question 7

How can excess glucose be stored?

Answer 7

As glycogen in the liver and muscle
As triacylglycerol’s in liver and adipose tissue

Question 8

Amino acids can be used as an energy source but aren’t usually unless in what state?

Answer 8

State of starvation

->excess amino acids stored as fat btw h.e. flashback xox

Question 9

The mechanism by which insulin is released depends on the activity of what?

Answer 9

The potassium ATP channels on the pancreatic beta cells

Question 10

When glucose is in abundance, how does it enter cells?

Answer 10

Via GLUT

Question 11

As glucose enters cells via GLUT, metabolism increases.
What happens when metabolism increases?

Answer 11

ATP increases within cells and the potassium ATP channel closes

Question 12

What happens after the ATP potassium channels close?

Answer 12

Intracellular potassium rises which depolarises the cell.
Voltage gated calcium channels open and trigger insulin exocytosis into circulation

->wordy but read through, should hopefully make sense

Question 13

Describe the mechanism of control of insulin.

(basically the last two flashcards together to give you the whole story)

Answer 13

Glucose enters cells via GLUT, metabolism increases.
ATP increases and ATP potassium channels close.
Intracellular potassium increases and depolarises the cell.
Voltage gated calcium channels open and trigger the exocytosis of insulin into the circulation.

Question 14

What is the primary action of insulin?

Answer 14

Lower blood glucose

Question 15

How does insulin lower blood glucose?

Answer 15

Binds to tyrosine kinase receptors on the cell membrane of insulin-dependant tissues.
This increases glucose uptake by these tissues.

Question 16

Which glucose transporters are insulin specific?

Answer 16

GLUT-4

Question 17

Describe how insulin enables the uptake of glucose by adipose and muscle.

Answer 17

Insulin stimulates the mobilisation of GLUT4 transporters so they can move from the cytoplasm to the membrane.
Now glucose can be transported into the cell.

Question 18

Most tissues do not require insulin to take up glucose. Which two tissues require insulin to uptake glucose?

Answer 18

Muscle
Adipose (fat) tissue

Question 19

GLUT-4 is the only insulin dependant glucose transporter. The others do not.
Where would you find GLUT-1 and GLUT-3 transporters?

Answer 19

Brain, kidney and RBC’s

Question 20

GLUT-4 is the only insulin dependant glucose transporter. The others do not.
Where would you find GLUT-2 transporters?

Answer 20

Beta cells of the pancreas and liver

Question 21

Why does the liver require insulin for glucose uptake if the liver is not an insulin-dependant tissue?

Answer 21

The liver gets glucose by GLUT-2 transporters which are insulin dependant

Question 22

As well as lowering BG, insulin increases glycogen synthesis in the muscle and liver. How?

Answer 22

Stimulated glycogen synthase and inhibits glycogen phosphorylase.

Question 23

List the additional actions of insulin as well as it’s primary role of lowering BG.

Answer 23

-Increases glycogen synthesis in muscle and liver AND inhibits glycogen phosphorylase.
-Increases amino acid uptake into muscle which promotes protein synthesis.
-Increases protein synthesis AND inhibits proteolysis
-Increases triacylglycerol synthesis AND inhibits lipolysis
-Inhibits enzymes of gluconeogenesis in the liver
-Has permissive effect on growth hormone

->I wouldn’t necessarily worry about remembering all the details, just read through and be aware of how insulin has additional roles in stimulating and inhibiting certain processes

Question 24

Glucagon increases insulin release too. This seems strange, but why does this occur?

Answer 24

Insulin is required to take up the glucose that is created via gluconeogenesis promoted by glucagon.
Otherwise, the glucose in blood would not be accessible to cells, muscle and adipose tissue.

Question 25

List some other GI related hormones which can increase the release of insulin.

Answer 25

Gastrin Secretin CCK ->these act as a warning to the pancreas to say there's a lot of glucose coming and currently being digested so the pancreas starts to secrete insulin ready

Question 26

Which nerve activity also increases insulin release?

Answer 26

Vagus nerve -> key nerve in controlling GI function and is similar to the hormones mentioned previously so pancreas knows there is a lot of glucose coming after digestion

Question 27

List some stimuli which inhibit the release of insulin.

Answer 27

Low BG levels Somatostatin Sympathetic alpha 2 mediated effects Stress e.g. hypoxia

Question 28

If giving insulin, would you get a greater increase if administrating it orally or via IV? Why?

Answer 28

Orally -> there would be increased insulin by direct effect of increase glucose on beta cells. This is the same if given I.V. However, if given orally, there is also vagal stimulation of B cells which will release incretin hormones (hormones which stimulate insulin secretion) Just read through:)

Question 29

Is glucagon an anabolic or catabolic hormone?

Answer 29

Catabolic

Question 30

Which type of hormone is glucagon?

Answer 30

Peptide hormone

Question 31

Which cells produce glucagon?

Answer 31

Alpha cells of pancreatic islet cells

Question 32

Where does glucagon mainly act upon?

Answer 32

The liver

Question 33

Which hormones are involved in the glucose counter-regulatory control system?

Answer 33

Glucagon Epinephrine Cortisol Growth hormone

Question 34

In which state of the body is glucagon most active?

Answer 34

Post-absorptive state

Question 35

What are the insulin receptors?

Answer 35

Tyrosine-kinase linked receptors

Question 36

What are the glucagon receptors?

Answer 36

G-protein coupled receptors

Question 37

The glucagon receptors, G-protein coupled receptors are linked to the adenylate cyclase/cAMP system, When activated, phosphorylate specific liver enzymes. This results in which processes?

Answer 37

1. Increased glycogenolysis (breakdown of glycogen) 2. Increased gluconeogenesis (formation of glucose) 3. Formation of ketones from fatty acids- lipolysis

Question 38

What is the storage form of glucose?

Answer 38

Glycogen

Question 39

Where can glucose be stored in the form of glycogen?

Answer 39

Muscle or liver

Question 40

What happens in glycogenolysis?

Answer 40

Glucagon stimulates the conversion of liver glycogen into free glucose

Question 41

The brain uses glucose for energy. However, what can it use if necessary?

Answer 41

Ketone bodies

Question 42

How can ketone bodies be produced?

Answer 42

Via beta-oxidation of free fatty acids

Question 43

What happens in terms of insulin and glucagon when there is an increase in glucose?

Answer 43

Increase in insulin Decrease in glucagon

Question 44

What happens in terms of insulin and glucagon when there is an decrease in glucose?

Answer 44

Increase in glucagon Decrease in insulin

Question 45

What is secreted when amino acids are in the plasma?

Answer 45

Both insulin and glucagon.

Question 46

Describe what would happen if we ate a meal high in protein with very little carbs.

Answer 46

Increased amino acids in plasma. Insulin stimulated to uptake amino acid. Decrease in blood glucose. Counteracted by simultaneous release of glucagon to maintain blood glucose levels.

Question 47

The brain gets priority over glucose for energy. What can most other tissues use instead for energy?

Answer 47

Free fatty acids Ketones

Question 48

List some stimuli which promote glucagon release.

Answer 48

-Low BG -High amino acid level in plasma -Sympathetic innervation and epinephrine -Cortisol -Stress e.g. exercise, infection

Question 49

Lit some of the stimuli which inhibit the release of glucagon.

Answer 49

-Glucose -Free fatty acids and ketones -Insulin -Somatostatin

Question 50

What happens to insulin level when there is an increase in parasympathetic activity?

Answer 50

Increase in insulin ->anticipation of digestion

Question 51

What happens when there is an increase in sympathetic activity?

Answer 51

Promotes glucose mobilisation therefore increase in glucagon and epinephrine. There will be inhibition of insulin.

Question 52

Name the four hormones which help to increase blood glucose.

Answer 52

Glucagon Epinephrine Cortisol Growth hormone ->the fact there are four really highlights the importance of maintaining blood glucose levels for brain function

Question 53

Which hormone antagonises the action of insulin?

Answer 53

Growth hormone

Question 54

The four hormones which help to raise blood glucose levels are known as the counter regulatory hormones. What do these hormones promote?

Answer 54

The formation of new glucose (gluconeogenesis) and break down of fatty adipose tissue (lipolysis)

Question 55

Which processes does glucagon stimulate?

Answer 55

Liver glycogenolysis Gluconeogenesis Lipolysis

Question 56

Which processes does epinephrine stimulate?

Answer 56

Muscle glycogenolysis Liver glycogenolysis Gluconeogenesis Lipolysis

Question 57

Which processes does cortisol stimulate?

Answer 57

Gluconeogenesis Inhibition of glucose uptake Lipolysis Protein catabolism

Question 58

Which processes does growth hormone stimulate?

Answer 58

Gluconeogenesis Inhibition of glucose uptake Lipolysis

Question 59

High levels of cortisol can lead to which disease?

Answer 59

Cushing's disease

Question 60

Which type of hormone is somatostatin?

Answer 60

Peptide hormone

Question 61

Which cells secrete somatostatin?

Answer 61

D cells of the pancreas

Question 62

What is the main function of pancreatic somatostatin?

Answer 62

Inhibit activity of the GIT

Question 63

Which condition can be helped by using synthetic somatostatin?

Answer 63

Life threating diahorrea ->this is because it slows gastric motility

Question 64

What does somatostatin suppress the release of?

Answer 64

Insulin and glucagon

Question 65

Patients with somatostatin releasing tumours will develop symptoms of which condition?

Answer 65

Diabetes ->this is because it supresses the release of insulin and glucagon

Question 66

In those with somatostatin secreting tumours, how do you get rid of the diabetes symptoms?

Answer 66

Removing the tumour

Question 67

Why does blood glucose increase in those with somatostatin secretin tumours despite the fact that the release of insulin AND glucagon is prevented?

Answer 67

Insulin is the only hormone which can reduce blood glucose. However, glucagon is only 1/4 which can raise levels hence why levels continue to rise and give diabetic symptoms

Question 68

Somatostatin released from the pancreas is identical to which hormone?

Answer 68

Growth inhibiting hormone released from the hypothalamus which can also be known as somatostatin

Question 69

Can insulin inhibit the release of glucagon?

Answer 69

Yes

Question 70

Can glucagon inhibit the release of insulin?

Answer 70

No- it stimulates it as the body needs to be able to take the glucose up