The Endocrine Pancreas - Part 1

Question 1

What is body energy equal to?

Answer 1

Energy intake - energy output

Question 2

What 2 hypothalamic centres determine energy intake by balance of activity?

Answer 2

Feeding centre - promotes feeling of hunger
Satiety centre - feeling of fullness by supressing feeding centre

Question 3

What is the glucostatic theory?

Answer 3

Food intake is determined by blood glucose
As BG conc. increases then drive to eat decreases

Question 4

What is lipostatic theory?

Answer 4

Food intake is determined by fat stores
As fat stores increase then drive to eat decreases
Leptin released by fat stores depresses feeding centres

Question 5

What are the 3 categories of energy output?

Answer 5

Cellular work
Mechanical work - regulated voluntarily by skeletal muscle
Heat loss - counts for half of energy output

Question 6

What are 3 elements of metabolism?

Answer 6

Extracting energy from nutrients in food
Storing that energy
Utilising that energy for work

Question 7

What is the definition of metabolism?

Answer 7

Integration of all biochemical reactions in the body

Question 8

What are anabolic and catabolic pathways?

Answer 8

Anabolic - build up, synthesis of large molecules from smaller for storage
Catabolic - break down, degradation of large molecules, releasing energy for work

Question 9

What type of phase is the post absorptive phase?

Answer 9

Catabolic

Question 10

What is an obligatory glucose utiliser?

Answer 10

Brain so BG conc. must be sufficient to supply brain even during fasted state
Failure causes hypoglycaemia

Question 11

What is the normal range of BG levels?

Answer 11

4.2-6.3mM
Hypoglycaemia is under 3

Question 12

What 2 endocrine hormones produced in pancreas maintain BG conc.?

Answer 12

Insulin and Glucagon

Question 13

What is stimulated by insulin?

Answer 13

Lipogenesis
Glycogenesis
Metabolism in most tissues

Question 14

What is stimulated by glucagon?

Answer 14

Glycogenolysis
Gluconeogenesis

Question 15

Where are endocrine hormones released in pancreas?

Answer 15

Islets of Langerhans

Question 16

What are the 4 types of islets cells?

Answer 16

Alpha
Beta
Delta
F cells

Question 17

What do alpha islets cells produce?

Answer 17

Glucagon

Question 18

What do beta islets cells produce?

Answer 18

Insulin

Question 19

What do delta islets cells produce?

Answer 19

Somatostatin

Question 20

What do F islets cells produce?

Answer 20

Pancreatic polypeptide

Question 21

What happens if there is more insulin than glucagon?

Answer 21

Glucose taken up by cells from plasma lowering BG conc.
Increases glucose oxidation, glycogen synthesis, fat synthesis and protein synthesis

Question 22

Describe insulin

Answer 22

Peptide hormone
Stimulates glucose uptake by cells
Only hormone which lower BG conc.

Question 23

How is insulin synthesised and secreted?

Answer 23

Large preprohormone - pre-proinsulin which converted to proinsulin in the ER
Packaged as granules in secretory vesicles
Cleaved again to give insulin and C peptide
Stored till activated B cell

Question 24

What stimulates release of insulin?

Answer 24

Mainly blood glucose conc.
Amino acids

Question 25

How is glucose stored?

Answer 25

Mainly energy source in absorptive state Excess stored as glycogen in liver and muscle And as TAG in liver and adipose tissue

Question 26

What is excess amino acids and fatty acids stored as?

Answer 26

Aa - converted to fat FA - triglycerides in adipose tissue and liver

Question 27

Describe the mechanism of control of insulin secretion by conc. of BG

Answer 27

Glucose is abundant so enters cells through GLUT and metabolism increases which increases ATP within cells Katp channels to close - intracellular K conc. rises so depolarises cell Voltage gated Ca channels open - trigger insulin vesicle exocytosis

Question 28

Describe low BG conc. and insulin secretion

Answer 28

Katp channels are open so K flows out of cells causing hyperpolarisation Voltage gated Ca channels remain closed and insulin not secreted

Question 29

What is the primary action of insulin?

Answer 29

Binds to tyrosine kinase receptors on cell membrane of insulin dependant tissues to increase glucose uptake In muscles and adipose tissue - stimulates specific GLUT4 which reside in cytoplasm

Question 30

What happens when GLUT4 is stimulated in muscle and adipose tissue?

Answer 30

Migrates to membrane and is able to transport glucose When stimulation by insulin stops then GLUT4 return to cytoplasm pool

Question 31

What tissues are insulin dependant?

Answer 31

Muscles and fat

Question 32

What GLUT transporters are not insulin dependant?

Answer 32

GLUT1 - basal glucose uptake in tissues GLUT2 - similar GLUT3 - b cells of pancreas and liver

Question 33

Describe liver and glucose uptake

Answer 33

GLUT2 transporters and is insulin independent Enters down conc. gradient Glucose transport into hepatocytes is affected by insulin status

Question 34

What happens in fed state in liver and glucose uptake?

Answer 34

Liver takes up glucose as insulin activates hexokinase which lowers glucose conc. in cells creating a gradient so movement in cells can happen

Question 35

What happens in fasted state in liver and glucose transport?

Answer 35

Liver synthesises glucose via glycogenolysis and gluconeogenesis Increases glucose conc. in cells so gradient favours glucose movement out of cell

Question 36

What are some of the the additional actions of insulin?

Answer 36

Increase glycogen synthesis and inhibits glycogen phosphorylase Promotes protein synthesis and inhibits proteolysis Increases lipogenesis and inhibits lipolysis Inhibits enzymes of gluconeogenesis Permissive effect on GH Promotes K ion entry stimulating NaKATPase

Question 37

What happens when insulin binds to tyrosine kinase receptor?

Answer 37

Receptor phosphorylates insulin receptor substrates (IRS) Second messenger pathways alter protein synthesis and existing proteins Membrane transport or cell metabolism changed

Question 38

What stimulates insulin release?

Answer 38

Increased BG conc. Increased aa conc. in plasma Glucagon Other hormones controlling GI secretion

Question 39

What stimuli inhibit insulin release?

Answer 39

Low BG conc. Somatostatin Sympathetic alpha-2 effects Stress - hypoxia

Question 40

Is IV or oral glucose has more insulin response?

Answer 40

Oral as increases insulin by direct effect in B cells and vagal stimulation of B cells plus incretin effects