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Flashcards in Phys of Endocrine Pancreas Deck (49):
1

What is the primary fuel for the body?

glucose

2

What is glucose stored as?

glycogen

3

Organs where glycogen is stored. (2)

-liver
-muscle

4

insulin is what type of hormone?

anabolic

5

What does it mean that insulin is an anabolic hormone?

it promotes the building of tissue stores

6

How can protein be used as an energy source?

amino acids can be changed to glucose in the liver and then used or stored as glycogen

7

gluconeogenesis

creating new glucose

8

glycogenolysis

the break down of glycogen stores

9

glycogenesis

formation of glycogen from sugar

10

glycolysis

breakdown of glucose

11

normal fasting blood glucose range

70-99 mg/dL

12

normal plasma postprandial glucose range

no higher than 140 mg/dl

13

what are the 4 counter regulatory hormones to insulin?

-glucagon
-epinephrine
-cortisol
-growth hormone

14

primary action of glucagon

-the major counter to insulin
-released when glucose concentrations fall too low
-exerts effect on liver to break down glycogen stores and release glucose into the blood rapidly
-predominant during fasting states

15

primary action of epinephrine

-stimulates the release of hepatic glucose via glycogenolysis and lipolysis
-released during periods of stress and emergency

16

primary action of cortisol

-stimulates hepatic uptake of amino acids
-can be used to make new glucose

17

primary action of growth hormone

-increase lipolysis
-inhibit glucose uptake at the muscle and adipose tissue

18

what are the 3 target organs of insulin action?

-liver
-muscle
-adipose tissue

(also the brain)

19

action of insulin on the liver

-liver is the first organ reached by insulin after being released into the portal circulation
-2 main actions:
1. simulate the uptake of glucose by the liver
2. stop the breakdown of glycogen by changing the enzymes in the glycogen synthesis pathway

-therefore, insulin stimulates glycogenesis, fatty acid synthesis, and triglyceride production and inhibits glycogenolysis, gluconeogenesis and ketogenesis

20

knowing the action of insulin on the liver, what happens at the liver when insulin levels are low?

the liver releases glucose from glycogen to maintain blood glucose w/i normal limits

21

action of insulin on the muscle

-stimulates the uptake of glucose and amino acids by the muscle cells
-promotes protein synthesis by increasing amino acid transport and stimulating ribosomal protein synthesis
-it also promotes glycogen synthesis to replace glycogen storage used during muscle activity

22

action of insulin on the adipose tissue

-stimulates glucose and fatty acid uptake leading to lipogenesis
-it inhibits lipolysis

23

what portion of the pancreas contains the exocrine cells?

head

24

what portion of the pancreas contains the endocrine cells?

tail

25

beta cells produce ?

insulin

26

alpha cells produce ?

glucagon

27

delta cells produce ?

somatostatin

28

define insulin

-protein made up of 51 amino acids
-it's a polypeptide whose genetic code is in the DNA located in the cell nucleus
-produced by the beta cells of the pancreas
-stored in the form of proinsulin in vacuoles until released

29

define proinsulin

-precursor to insulin
-polypeptide of 86 amino acids
-produced and stored in secretory granules (made by Golgi)

30

define C peptide

-the counter part of insulin that is produced when proinsulin is cleaved
-it has no biological activity but is still released into the portal vein in equimolar amounts to insulin
-therefore is easy to measure

31

define basal insulin

-the insulin that is secreted by the pancreas at all times
-it helps the peripheral tissues take up glucose during fasting periods

32

first phase of insulin release from the pancreas

-quick rise in insulin concentrations in response to rising glucose concentrations
-the readily available insulin is rapidly depleated
-the rapid rise in insulin goes directly to the liver to signal it to quit breaking down glycogen
-so, first phase = decrease in hepatic glucose production

33

second phase of insulin release from the pancreas

-somewhat delayed
-represents a more slowly mobilized pool of insulin in the beta cells
-the insulin not taken up by the liver enters the peripheral circulation where glucose is entering from the intestines
-they travel together until they reach muscle and adipose tissue

34

what happens to glucose in a fed state?

-it is absorbed from the intestines and enters the blood stream
-increase in glucose concentration stimulates the release of insulin from beta cells
-as glucose reenters circulation of the GI tract, insulin acts to restrain the rise in blood glucose concentration

35

what happens to insulin in the fed state?

-insulin release is stimulated by rising glucose concentrations
-it then uses two processes to keep the blood glucose concentration from rising:
1. suppression of hepatic glucose output
2. stimulation of glucose uptake via muscle and liver

36

overview summary of insulins action in the fed state

-suppress hepatic glycose production
-stimulate glucose uptake by peripheral tissues
-suppress glucagon release
-muscle uptake of glucose
-decrease in lipolysis and increase in lipogenesis
-increased amino acid uptake by muscles leading to increased protein synthesis

37

action of insulin in a fasting state

-glucose concentrations fall resulting in a decrease in the plasma insulin concentration
-80% glucose disposal happens in non-insulin dependent tissues (brain, blood, neurons, etc.)
-remaining 20% of glucose metabolism occurs in the liver, muscle, and adipose
-inulin is released in a pulsatile pattern throughout the day when a person is not eating (basal insulin)

38

action of glucagon in a fasting state

-glucagon is secreted by pancreatic alpha cells to oppose the action of insulin and stimulate hepatic glucose production and glycogenolysis
-glucagon promotes availabilyt of energy in the form of glucose from glycogen and ketones

39

what is the relationship b/w glucagon and insulin?

-they are closely linked
-one increases while the other decreases to keep plasma glucose levels normal

40

describe the interaction of insulin w/ its receptor

-receptor is on target tissues cell membrane
-has alpha and beta subunits
-insulin binds alpha unit which activates the beta subunit
-result is recruitment and phosphorylation of intracellular substrates
-triggers a cascade of events in the cells leading to activation of GLUT4 moving to cell membrane, binding with extracellular glucose and transporting it into the cell

41

what is the role of the liver in the metabolism of insulin?

-liver removes 50% of insulin on first pass
-liver is major site of endogenous insulin elimination

42

what is the role of the kidneys in the metabolism of insulin?

-2nd major site of insulin metabolism next to the liver
-in those w/ renal insufficiency or failure, the half life of insulin will be prolonged

43

action of glucagon

-secreted as insulin levels fall
-inhibited by glucose
-major target organ = liver
-stimulates breakdown of glycogen stores to maintain glucose levels during fasting state

44

action of somatostatin

-produced by delta cells
-inhibits secretion of many other hormones
-in pancreatic islet: inhibits secretion of insulin and glucagon

45

action of amylin

-co-packaged and co-secreted w/ insulin from beta cells
-helps regulate postprandial glycemia by suppressing postmeal glucagon secretion of alpha cells
-helps coordinate storage of carbs to transfer triglyceride into muscle glycogen in skeletal muscle

46

describe the incretin effect

-incretins = GLP-1 and GLP-2
-GLP-1: produced by L cells in the intestines after a meal
-stimulates the production of insulin and inhibits secretion of glucagon; inhibits gastric emptying; inhibits appetite and induces weight loss
-GLP-2: stimulates nutrient absorption at the intestines

47

enzyme that inactivates incretins

depeptidyl peptidase IV (DPP-IV)

48

effect of PSNS on insulin secretion

-stimulates insulin secretion
-"cephalic phase"
-sensory stimuli and neural inputs are activated when food is eaten or anticipated
-Vagus nerve activation --> stimulates insulin secretion

49

effect of SNS on insulin secretion

-inhibits insulin secretion