The Endocrine Pancreas 1 Flashcards
What is the function of the feeding centre?
promotes feelings of hunger and drive to eat
Whats the function of the Satiety Centre?
promotes feelings of fullness by suppressing the Feeding Centre
What is glucostatic theory?
Food intake determined by [BG], as it increases, drive to eat decreases
What is lipostatic theory?
Food intake determined by fat stores, as they increase, drive to eat decreases
What peptide hormone is released by fat stores to depress feeding?
Leptin
What are the 3 categories of cellular work?
Cellular work
Mechanical work
Heat loss
What are the 3 elements of human metabolism?
Extracting energy from nutrients
Storing said energy
Utilising said energy for work
What are anabolic pathways?
Net effect is synthesis of large molecules from smaller ones
What are catabolic pathways?
Breaking down large molecules to smaller ones - releasing energy
What is an absorptive state?
After eating - ingested nutrients supply the energy needs of the body (anabolic)
What is a fasted/post-absorptive state?
Between meals - body relies on stores for energy (catabolic)
What has the first dibs on glucose?
The brain
What is glycogenolysis?
Glycogen -> glucose
What is gluconeogenesis?
Amino-acids -> Glucose
How is excess glucose removed?
Via urine
What hormone is essential for uptake of [BG]?
Insulin
What is lipogenesis?
Turning excess glucose into fat stores
What is the normal range of [BG]?
4.2-6.3mM
Where is insulin produced?
Islet of Langerhans (pancreas)
What do alpha cells produce?
Glucagon
What do beta cells produce?
Insulin
What do delta cells produce?
Somatostatin
What do F cells produce?
Pancreatic polypeptide
What are the effects of increased (dominant) insulin?
(glucose taken up by cells) ↑ Glucose oxidation ↑ Glycogen synthesis ↑ Fat synthesis ↑ Protein Synthesis
What are the effects of increased (dominant) glucagon?
(glucose released into plasma)
↑ Glycogenolysis
↑ Gluconeogenesis
↑ Ketogenesis
What type of hormone is insulin?
Peptide hormone
Where is insulin made?
Beta cells in islets of langerhans
How is insulin synthesised?
Preprohormone - Preproinsulin
What is the fate of preproinsulin?
Converted into proinsulin in the endoplasmic reticulum
What is the fate of proinsulin?
Packaged as granules in vesicles where it is cleaved into insulin and C-peptide and stored
How is insulin unique relating to glucose?
It is the only hormone which lowers [BG]
How does [BG] trigger insulin secretion from beta cells?
[BG] enters cells through GLUT and increases metabolism
Increased [ATp} causes the Katp channel to close
Closing the Katp channel causes ↑[K+], depolarising the cell
This opens voltage gated Ca2+ channels
Triggers vesicle exocytosis
How does low [BG] trigger low insulin?
ATP is low so Katp channels are open, removing the K+, thus the +ve charge
What does insulin bind to?
Kinase receptors on insulin sensitive tissues
Insulin stimulates the mobilisation of what when bound?
GLUT-4 transporters to migrate to the membrane
What types of tissue are insulin dependent?
Fat
Muscle
Which GLUT transporters are NOT insulin dependent?
GLUT-1, 2, 3
What is the role of GLUT-1?
Glucose uptake in brain, kidney, RBC
What is the role of GLUT-2?
Glucose uptake in Pancreas, liver
What is the role of GLUT-3?
Glucose uptake in brain, kidney, RBC
How does the liver take up glucose?
GLUT-2 and 4
Glucose enters down the concentration gradient
(transport into hepatocytes is affected by insulin)
How does the liver continue to uptake glucose in a fed state?
Insulin activates Hexokinase which converts Glucose -> G-6-P
Relatively decreasing [Glucose]
What is the role of the liver on [Glucose] in a fasted state?
Glucose synthesis (gluconeogenesis, glycogenolysis) which ↑[Glucose] causing it to move out the cell
What is the non-anabolic role of insulin?
Promote K+ entry into cells stimulating Na+/K+ ATPase
What are the anabolic roles of insulin?
Increase glycogen synthesis in muscles and liver Inhibit glycogen phosphorylase Increase AA uptake Promote protein synthesis Increase TAG synthesis Inhibit enzymes of gluconeogenesis
What is the half life of insulin?
~5mins
What happens to insulin after it completes its action?
Internalised with the receptors by endocytosis
Destroyed by insulin protease or recycled
What are the stimuli which increase insulin release?
Increased [BG] Increased [Amino A]plasma Glucagon Incretin hormones controling GI secretion & motility Vagal nerve activity
What are the stimuli which inhibit insulin release?
Low [BG]
Somatostatin (GHIH)
Sympathetic alpha2 effects
Stress
Why does oral loading glucose stimulate a larger insulin response than I.V glucose?
Increase insulin by effect on beta cells AND Vagal stimulation via anticipatory effect PLUS Incretin!
