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ENDO > Pancreas anatomy and pysiology > Flashcards

Pancreas anatomy and pysiology Flashcards

1
Q

What does the exocrine pancreas do?

A

Secrete bicarbonate

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2
Q

Describe the exocrine pancreas

A
  • It is the larger component of the pancreas
  • Secretes digestive enzymes
  • Secretes bicarbonate (base) to neutralise acid produced in the stomach
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3
Q

What stimulates the pancreas to secrete digestive enzymes?

A

Gastrointestinal hormones e.g. Cholecystokinin

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4
Q

List the digestive enzymes and what they act on

A
  • Trypsin/ carboxypeptidase= proteins
  • Ribonuclease= RNA
  • Deoxyribonuclease= DNA
  • Amylase= starch
  • Lipase= triglycerides
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5
Q

Describe the 3 types of islet cell in the endocrine pancreas

A
  • Beta cells= insulin
  • Alpha cells= glucagon
  • Delta cells = somatostatin
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6
Q

Describe somatostatin

A
  • Produced by the hypothalamus, stomach, intestine and pancreas
  • Supresses insulin and glucagon
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7
Q

Describe insulin

A
  • Peptide hormone (so can’t give orally as digestive juices won’t break it down)
  • Secreted by B cells
  • Prohormone= proinsulin
  • Intracytoplasmic pool of proinsulin (vesicles stored in cytoplasm)
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8
Q

Describe C-protein

A

The c-protein must be removed from the proinsulin before the insulin can be secreted.
C-protein is released at same rate as insulin but it is eliminated a lot slower so is useful to measure to check levels of insulin secretion.

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9
Q

Discuss the structure of insulin

A

2 polypeptide chains connected by 2 disulphide bonds

-Degraded in liver or kidney via cleavage of the disulphide bonds

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10
Q

Discuss insulin kinetics

A
  • Secreted from pancreas
  • Plasma half life=5-8 minutes
  • Enters portal system and sent to liver
  • ACTS ON LIVER FIRST
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11
Q

Describe the 3 mechanisms used to regulate insulin

A

1) Nutrients: Glucose and Aa
2) Gastrointestinal hormones: e.g. gastric inhibitory peptide (GIP)
3) ANS (parasympathetic stimulates/ sympathetic inhibits)

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12
Q

State the effect of incretins on insulin

A

-Incretins increase insulin secretion, we want insulin to be produced whilst eating a meal so the products can be stored and saved for when needed.

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13
Q

How is insulin secreted?

A

-Via calcium mediated exocytosis

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14
Q

Describe the first and second phases of insulin secretion

A
  • First phase= release of the intracytoplasmic pool of proinsulin
  • Second phase= insulin secretion results from new protein synthesis
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15
Q

Describe the release of insulin

A
  • Blood glucose increases
  • GLUT2 transporters allow glucose into cell
  • Glucose is phosphorylated by glucokinase (traps the glucose in the cell)
  • Increase in ATP production
  • Inhibits ATP-sensitive potassium channels
  • Increased intracellular potassium concentration leads to depolarisation
  • Voltage gated calcium channels activated
  • Influx of calcium triggers exocytosis of insulin
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16
Q

When insulin binds to a receptor on the plasma membrane, what signalling transduction pathway is triggered?

A

Tyrosine kinase

17
Q

What effect does insulin have on GLUT4 transporters?

A

Insulin stimulates translocation of GLUT4 from the cytoplasmic membrane to the plasma membrane
-GLUT4 proteins are insulin responsive glucose transporters

18
Q

Where are GLUT4 proteins found?

A

In skeletal muscle and adipose tissue

19
Q

What does GLUT2 do?

A

Senses glucose in the pancreas whereas GLUT4 helps insulin in other tissues by getting glucose into cells.
( also GLUT2 in liver as NO GLUT4)

20
Q

How does insulin work in the brain?

A

-No GLUT4- insulin independent GLUT1 transporter

21
Q

Why does polyphagia occur in cases of diabetes mellitus?

A
  • Insulin is needed for the satiety centre to uptake glucose

- The low insulin in diabetes mellitus means satiety isn’t met and appetite increases.

22
Q

Discuss insulin and hormone sensitive lipase

A

-Insulin inhibits HSL-> decreases lipolysis

Stimulates de novo lipogenesis

23
Q

What is de novo lipogenesis?

A

Production of fatty acids from glucose

24
Q

What does HSL do?

A

Increases delivery of fat to tissues

25
Q

Where is glucagon metabolised?

A

Liver and kidney

26
Q

Is glucagon catabolic or anabolic?

A

Normally catabolic

27
Q

Where is glucagon’s main site of action?

A

The liver

28
Q

What does glucagon stimulate?

A

Glycogenolysis

Gluconeogenesis

29
Q

What stimulates/ inhibits glucagon?

A
  • Inhibited by high blood glucose

- Stimulated by high amino aicd levels

ENDO (39 decks)

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