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endocrine 1 > Phys of Endocrine Pancreas > Flashcards

Phys of Endocrine Pancreas Flashcards

1
Q

What is the primary fuel for the body?

A

glucose

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2
Q

What is glucose stored as?

A

glycogen

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3
Q

Organs where glycogen is stored. (2)

A
  • liver

- muscle

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4
Q

insulin is what type of hormone?

A

anabolic

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5
Q

What does it mean that insulin is an anabolic hormone?

A

it promotes the building of tissue stores

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6
Q

How can protein be used as an energy source?

A

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

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7
Q

gluconeogenesis

A

creating new glucose

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8
Q

glycogenolysis

A

the break down of glycogen stores

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9
Q

glycogenesis

A

formation of glycogen from sugar

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10
Q

glycolysis

A

breakdown of glucose

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11
Q

normal fasting blood glucose range

A

70-99 mg/dL

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12
Q

normal plasma postprandial glucose range

A

no higher than 140 mg/dl

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13
Q

what are the 4 counter regulatory hormones to insulin?

A
  • glucagon
  • epinephrine
  • cortisol
  • growth hormone
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14
Q

primary action of glucagon

A
  • 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
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15
Q

primary action of epinephrine

A
  • stimulates the release of hepatic glucose via glycogenolysis and lipolysis
  • released during periods of stress and emergency
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16
Q

primary action of cortisol

A
  • stimulates hepatic uptake of amino acids

- can be used to make new glucose

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17
Q

primary action of growth hormone

A
  • increase lipolysis

- inhibit glucose uptake at the muscle and adipose tissue

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18
Q

what are the 3 target organs of insulin action?

A
  • liver
  • muscle
  • adipose tissue

(also the brain)

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19
Q

action of insulin on the liver

A
  • 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

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20
Q

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

A

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

21
Q

action of insulin on the muscle

A
  • 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
Q

action of insulin on the adipose tissue

A
  • stimulates glucose and fatty acid uptake leading to lipogenesis
  • it inhibits lipolysis
23
Q

what portion of the pancreas contains the exocrine cells?

A

head

24
Q

what portion of the pancreas contains the endocrine cells?

A

tail

25
Q

beta cells produce ?

A

insulin

26
Q

alpha cells produce ?

A

glucagon

27
Q

delta cells produce ?

A

somatostatin

28
Q

define insulin

A
  • 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
Q

define proinsulin

A
  • precursor to insulin
  • polypeptide of 86 amino acids
  • produced and stored in secretory granules (made by Golgi)
30
Q

define C peptide

A
  • 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
Q

define basal insulin

A
  • the insulin that is secreted by the pancreas at all times

- it helps the peripheral tissues take up glucose during fasting periods

32
Q

first phase of insulin release from the pancreas

A
  • 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
Q

second phase of insulin release from the pancreas

A
  • 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
Q

what happens to glucose in a fed state?

A
  • 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
Q

what happens to insulin in the fed state?

A
  • 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
Q

overview summary of insulins action in the fed state

A
  • 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
Q

action of insulin in a fasting state

A
  • 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
Q

action of glucagon in a fasting state

A
  • 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
Q

what is the relationship b/w glucagon and insulin?

A
  • they are closely linked

- one increases while the other decreases to keep plasma glucose levels normal

40
Q

describe the interaction of insulin w/ its receptor

A
  • 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
Q

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

A
  • liver removes 50% of insulin on first pass

- liver is major site of endogenous insulin elimination

42
Q

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

A
  • 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
Q

action of glucagon

A
  • 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
Q

action of somatostatin

A
  • produced by delta cells
  • inhibits secretion of many other hormones
  • in pancreatic islet: inhibits secretion of insulin and glucagon
45
Q

action of amylin

A
  • 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
Q

describe the incretin effect

A
  • 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
Q

enzyme that inactivates incretins

A

depeptidyl peptidase IV (DPP-IV)

48
Q

effect of PSNS on insulin secretion

A
  • 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
Q

effect of SNS on insulin secretion

A

-inhibits insulin secretion

endocrine 1 (18 decks)

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