The Pancreas (4-6) Flashcards

Question

What are the hormones of the islet of Langerhans?

Answer 1

Beta-cell → insulin Alpha-cell → glucagon Delta-cell → somatostatin → islets are vascularised for secretion of hormones into blood

Answer 2

Islet cells don't only do endocrine signalling → beta cell - autocrine, paracrine etc

Answer 3

Preprohormone → processed differently in islet alpha cells in the gut and brain → only a small part makes glucagon → mediated by enzymes that cleave at particular sites

Answer 4

There is blood flow through the islet → can go through the venules and signal to other side of islet

Answer 5

Inhibitory via activation of SSTR2 and 5 → inhibits adenylate cyclase and reduce cAMP → open K+atp and hyper polarise the membrane - can't get Ca2+ in, prevents vesicles of insulin docking

Answer 6

Anabolic (fed state) Amino acids → protein biosynthesis Glucose → glycogenesis Fatty acids → lipogenesis

Answer 7

Catabolic (starved state) Glycogenolysis, lipolysis, ketogenesis, gluconeogenesis → fuel production

Answer 8

High presence of insulin drives uptake of amino acids in the liver → increases protein synthesis → decreases protein breakdown

Answer 9

Stored form of glucose → made from glucose-1-p by glycogen synthase → glycogen phosphorylase converts glycogen back to glucose-1-p

Answer 10

Drives formation of glycogen Synthase phosphate can activate glycogen synthase → insulin up regulates synthase phosphatase → also removes phosphate from glycogen phosphorylase promoting glycogen formation Protein kinase can remove active part of glycogen synthase → insulin down regulates protein kinase

Answer 11

Inhibits formation of glycogen Glucagon/epinephrine increases cAMP cAMP stimulates phosphorylase kinase which activates glycogen phosphorylase → promoting conversion of glycogen to glucose-1-phosphate cAMP stimulates protein kinase A which inactivates glycogen synthase → inhibiting glycogen synthesis, promoting glucose-1-p

Answer 12

Insulin binds its receptor in plasma membrane → IRS-1 binds the phosphorylated tyrosines of the activated receptor → activates the PKB/Akt pathway Signal cascades leads to: → activating glycogen synthase - activate the activator → inhibiting glycogen phosphorylase - inactivates the inactivator → inhibiting of a glycogen synthase inhibitor Drives glycogen synthesis

Answer 13

Fat cell lipoprotein lipase actively promoted by insulin → fat synthesis Insulin also up regulates formation go glucose into pentose shunt and alpha-glycerophosphate for fat synthesis Insulin enables triglyceride formation

Answer 14

Glucagon down-regulates fat cell lipoprotein lipase → inhibiting fat synthesis → in a starved state you don't want to store fat in adipose tissue Glucagon up regulates hormone sensitive lipase → drives freeing of fatty acids

Answer 15

Glycolysis flux is controlled by: → availability of substrate → conc of enzymes responsible for rate-limiting steps → allosteric regulation of enzymes → covalent modification of enzymes Insulin up regulates glycolysis

Answer 16

Gluconeogenesis → allows formation of glucose from e.g. pyruvate, glycerol Down regulated by insulin

Answer 17

Lack of insulin means you can't move glucose in → decreases glucose utilisation → increases protein catabolism - aminoacidaemia → increases gluconeogenesis - hyperglycaemia → increases urinary nitrogen → causes intracellular dehydration - thirst, coma, death → K+ is lost from cells - increases K+ loss from body - hyper polarisation of cells

Answer 18

Insulin deficiency → causes increased ketone bodies - diabetic ketoacidosis

Answer 19

Insulin dependant - insufficient production of insulin → usually <30yrs, juvenile onset → 10% of diabetics

Answer 20

Non-insulin dependent → pancreas functions normally, but there is insulin resistance → its an epidemic → closely linked with obesity

Answer 21

A decrease in receptors/receptor binding → 90% develop compensatory increases in beta-cell mass and hyperinsulinemia → 10% develop beta-cell failure and diabetes

Answer 22

Atypical form of type II diabetes → usually develops before the age of 25 → inherited in an autosomal dominant fashion (unlike type II) → several genetic defects described

Answer 23

Pregnancy related diabetes → caused by placental normal interference (human placental lactose, growth hormone) → progesterone indirect effects → insulin resistance - reduce Tyr-P, increased Ser-P - results in reduces insulin signals can lead to abnormally large foetus, increased rate of spontaneous abortion, increased risk of congenital abnormalities, neonatal hypoglycaemia

Answer 24

→ elevated blood glucose, loss of glucose in urine → dehydration, increased thirst → inability to use glucose energy - fatigue, nausea → more prone to infection → blurred vision → extreme - diabetic coma

Answer 25

→ blindess - diabetic retinopathy → kidney failure → nerve damage → atherosclerosis → stroke → coronary heart disease → coma

Answer 26

Diet, weight reduction and exercise, increase body's sensitivity to insulin, insulin Medication Transplantation

Answer 27

1921 - Banting and Best isolated insulin Isolated ‘isletin’ from degenerating ligated pancreas - reinjected into diabetic dogs - enzymes don’t go into duodenum, stay in pancreas - degrade - secretion of islet enough to replace pancreas function