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GIT physiology > Endocrinology > Flashcards

Endocrinology Flashcards

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1
Q

Regarding metabolism in the fed state, where are glucose and AAs transported

A

From intestine to the blood

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2
Q

Regarding metabolism in the fed state, where are dietary lipids transported

A

From the lymphatic system to the blood

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3
Q

What does insulin stimulate

A

Storage of fuels and synthesis of proteins

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4
Q

What is the fuel reserve of a well-fed human

A

161,000 kcal

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5
Q

Energy needed for a 24 hr period

A

1600-6000 kcal

  • sufficient reserves for starvation up to 1-3 months
  • however glucose reserves are exhausted < 1 day
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6
Q

Even under starvation what must the blood-glucose level be above

A

40 mg/100 ml

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7
Q

In prolonged starvation, what is the first priority

A

Sufficient glucose for brain, nervous tissue, RBC

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8
Q

In prolonged starvation, what is the 2nd priority

A

Preserve protein - lipolysis & gluconeogenesis

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9
Q

After 3 days of starvation what do the brain and heart start to do

A

Use ketones as fuel

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10
Q

After several weeks of starvation, what is the major fuel of the brain

A

Ketone bodies

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11
Q

What happens when TAG stores must be used (prolonged starvation)

A

Increase protein degraded

Decrease heart, liver and kidney function

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12
Q

What happens to 1. Glucose 2. Ketone body and 3. FA conc in plasma during starvation

A
  1. Decreases but remains above 3-4 mM
  2. Increases rapidly
    3, Increases slowly
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13
Q

Decreasing order of total body metabolic fuel

A
  1. Fat
  2. Protein
  3. Muscle glycogen
  4. Hepatic glycogen
  5. Circulating nutrients
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14
Q

Decreasing order of circulating fuel

A
  1. glucose

2. TAGs & free FAs

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15
Q

What is the exocrine pancreas associated with

A

Acini - digestion (99%)

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16
Q

What is the endocrine pancreas associated with

A

Islets of Langerhans - control of blood glucose (1%)

17
Q

What do the beta cells of the islets of langerhans release

A

Insulin (see photo)

18
Q

What do the alpha cells of the islets of langerhans release

A

glucagon (see photo)

19
Q

What do the gamma cells of the islets of langerhans release

A

Somatostatin

20
Q

Where are pancreatic polypeptides found and what do they do

A

Found between acinar cells and inhibit pancreatic secretion of fluid

21
Q

What is optimal blood glucose concentration

A

Normal fasting level = 90-100mg/100 mls (5mM)

22
Q

Effect of an increase in glucose on insulin

A

Increased insulin

23
Q

Effect of a decrease in glucose on insulin

A

Decreased insulin

24
Q

Vascularisation of islets

A

Richly vascularised

- 1-2% of pancreas but 10-15% pancreatic blood flow

25
Q

Effect of increasing plasma AAs on insulin

A

Large increase in insulin

26
Q

Effect of increasing free FAs on insulin

A

Increase in insulin

27
Q

Effect of increasing Glucagon on insulin

A

Increase in insulin

28
Q

Effect of increasing GH & GIT hormones on insulin

A

Increase in insulin

29
Q

What are the islets modulated by

A

ANS innervation - modulate insulin and glucagon secretion

30
Q

Which has a greater effect - orally administered glucose or IV administered glucose

A

Orally administered

- glucagon, glucagon derivatives, secretin, cholecystokinin & gastric inhibitory peptide stimulate insulin secretion

31
Q

What is the incretin effect

A

Gut-derived factors that enhance glucose-stimulated insulin secretion from the islet beta-cell
ie a graph re-iterating that oral glucose has a greater effect than IV glucose infusion

32
Q

Where is Glucagon-like polypeptide 1 (GLP-1) synthesised

A

Within L cells located predominantly in ileum and colon & a lesser number in the duodenum and jejunum

33
Q

What does GLP-1 do

A
  • stimulates insulin secretion
  • suppresses glucagon secretion
  • slows gastric emptying
  • reduces food intake
  • increases beta cell mass
  • maintains beta cell function (decreases beta cell apoptosis)
  • improves insulin sensitivity (muscle)
  • enhances glucose disposal (decreases glucose production in liver)
  • Increases cardiac protection and CO
  • decreases appetite
  • increases neuroprotection
34
Q

What effect of GLP-1 is preserved in type 2 diabetes

A

Glucose lowering effects

35
Q
  1. Tissue distribution & 2. Special properties of GLUT 1
A
  1. Most cells
  2. High capacity
    Relatively low Km (5mM) => high substrate affinity
36
Q
  1. Tissue distribution & 2. Special properties of GLUT 2
A 
1. Liver
beta cells
hypothalamus
basolateral membrane of SI
2. High capacity but low affinity => high Km (15-20mM)
Part of the glucose sensor in beta-cells
37
Q
  1. Tissue distribution & 2. Special properties of GLUT 3
A
  1. Neurons
    Placenta
    testes
  2. Low Km (1mM) and high capacity
38
Q
  1. Tissue distribution & 2. Special properties of GLUT 4
A 
1. Skeletal muscle
Cardiac muscle
Fat
2. Activated by insulin
Km = 5mM
39
Q
  1. Tissue distribution & 2. Special properties of GLUT 5
A
  1. SI mucosal surface
    sperm
  2. Primarily fructose carrier in intestine

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