Gastrointestinal hormones

Question 1

What do GI hormones regulate?

Answer 1

Feeling of hunger, motility, insulin release, secretion (of gastric acid, digestive enzymes)

Question 2

Describe how most GI hormones begin as?

Answer 2

Larger precursors (often from same preprohormone product)

Question 3

Why do GI hormones have short half life?

Answer 3

Inactivation and cleavage by peptidases (3-5mins)

Question 4

Where are gut endocrine cells found?

Answer 4

Scattered in gut epithelium in crypts in villi

Question 5

Describe structure of gut endocrine cells

Answer 5

Most have microvilli on apex opening to gut lumen (sense its contents)

Nutrient sensing apical GPCRs

Question 6

What do gut endocrine cells sense/respond to?

Answer 6

Respond to carbs, bile salts lipids and proteins

Question 7

From which surface of endocrine cells are gut hormones released?

Answer 7

Basally

Question 8

What are the different routes for gut endocrine secretions?

Answer 8

Endocrine/paracrine, neuroendocrine (enteric nervous system)

Question 9

What stimulates release of gut hormones?

Answer 9

Mechanical/electrical presence of food

Cephalic phase

Question 10

What region(s) are hormones released from? What is the most common?

Answer 10

Stomach, duodenum, and colon

Small intestine is the most common

Question 11

What mechanism releases peptide hormones?

Answer 11

Exocytosis

Question 12

What layer are gut endocrine cells derived from?

Answer 12

Endoderm

Question 13

What 2 structures release peptide hormones?

Answer 13

Gut endocrine cells

Nerves of ENS (endocrine)

Question 14

Integrated role of gut endocrine and nervous systems…

Answer 14

Control motor/digestive/vascular activity of the gut

Question 15

What are 2 families of gut hormones?

Answer 15

Gastrin like and secretin like

Question 16

Example of gastrin like hormones

Answer 16

Gastrin, CCK

Question 17

Example of secretin like hormones

Answer 17

VIP, secretin, GIP, glucagon

Question 18

Which hormones regulate digestion (4)?

Answer 18

Histamine, somatostatin, secretin, gut glucagon

Question 19

What hormone regulates digestion and appetite (1)?

Answer 19

CCK

Question 20

What do the incretin hormones do, give an example?

Answer 20

Regulate insulin secretion

GIP and GLP1

Question 21

Which hormones are released in stomach?

Answer 21

Histamine, gastrin, ghrelin and somatostatin

Question 22

What hormone is released by duodenum?

Answer 22

Gastrin

Question 23

What hormones are released by small intestine and colon?

Answer 23

VIP, CCK, PYY, GIP, GLP1

Question 24

What cell makes histamine?

Answer 24

ECL cells of stomach

Question 25

What is histamine made from, and how (enzyme)?

Answer 25

Histidine by histidine decarboxylase

Question 26

What stimulates histamine release

Answer 26

Gastrin, vagal stimulation, and stretch

Question 27

What are the actions of histamine?

Answer 27

Local paracrine action stimulate HCl secretion via H2 receptors on parietal cell

Question 28

What receptor and what cell does histamine act on?

Answer 28

H2 receptor on parietal cells

Question 29

Where is Gastrin synthesised?

Answer 29

G cells of gastric antrum crypts and duodenal cells

Question 30

What factors stimulate gastrin secretion (4)?

Answer 30

Luminal protein digestion products (e.g. AA) Vagus (via ACh + gastrin release peptide) Stomach distention Hypercalcaemia

Question 31

What inhibits gastrin release?

Answer 31

Stomach pH<2.5 (H+ -ve feedback) Somatostatin (and secretin)

Question 32

What part of stomach makes gastrin?

Answer 32

Gastric antrum

Question 33

What are the actions of gastrin (5)?

Answer 33

Stimulate gastric acid secretion via insertion of K+/H+ ATPase into apical membrane of parietal cells Parietal cell growth Pepsinogen secretion secretion Antral motility and mucosal blood flow Water and electrolyte secretion in liver, pancreas and intestine

Question 34

How does gastrin stimulate gastric acid secretion (2 ways)?

Answer 34

Directly via binding to parietal cell to induce apical expression of K+/H+ATPase Indirectly binding to ECL cells to induce release of histamine (which acts on H2)

Question 35

What receptor does gastrin bind to on parietal cells?

Answer 35

CCK-B

Question 36

What are ECL cells?

Answer 36

Enterochromaffin-like cells or ECL cells are a type of neuroendocrine cell secreting histamine.

Question 37

Where is secretin made?

Answer 37

From duodenum to ileum (S cells in the neck of crypts)

Question 38

What cells secrete secretin?

Answer 38

S cells

Question 39

Describe distribution of S cells from duodenum to distal ileum?

Answer 39

Fewer

Question 40

What stimulates secretin release?

Answer 40

Acid in proximal duodenum

Question 41

What inhibits secretin release?

Answer 41

Somatostatin

Question 42

What are the effects of secretin?

Answer 42

Stimulate pancreatic secretions of HCO3- and water (wash pancreatic enzymes into gut) Stimualte liver secretion of HCO3- and water into bile (potentiate CCK, calcitonin PTH secretion) Controlling gut pH Reduces acid secretion by parietal cells of the stomach.

Question 43

Which gut hormone is important for controlling gut pH?

Answer 43

Secretin

Question 44

How does secretin reduce acid secretion by the stomach parietal cells?

Answer 44

Stimulating release of somatostatin Inhibiting release of gastrin in the pyloric antrum Direct downregulation of the parietal cell acid secretory mechanics.

Question 45

What cells secrete somatostatin, where?

Answer 45

D cells in gastric antrum to colon

Question 46

What is the function of somatostatin?

Answer 46

Suppresses secretion of GI hormones Suppresses their effects (acid etc) Retards absorption glucose (protects against post-prandial hyperglycaemia)

Question 47

Where is VIP released?

Answer 47

Enteric neurons in pelvic parasympathetic nerves also in brain and in nerves in pancreas

Question 48

What triggers VIP release

Answer 48

Unknown: not food releated

Question 49

What triggers somastatin release?

Answer 49

Stimulated by meals: amino acids, glucose, fatty acids, gastrin, secretin.

Question 50

What does VIP do?

Answer 50

Relaxes cardiac sphincter, stomach, anal sphincter; vasodilator. Causes pancreatic bicarbonate secretion.

Question 51

What cells secrete motilin ?

Answer 51

Mo cells from antrum to colon

Question 52

What is motilin thought to be involved with?

Answer 52

Initiating the MMC (migrating myoelectric motility complex)

Question 53

What cells secret gut glucagon and where?

Answer 53

Gastric A cells Ilial, colonic L cells

Question 54

What effect does gut glucagon have?

Answer 54

Stimulates gastric/intestinal motility, stimulates intestinal absorption sugars, systemic glucagon-like effects.

Question 55

Where is CCK made?

Answer 55

I cells in duodenum and jejunum

Question 56

What stimulates release of CCK?

Answer 56

Protein and fat digestion products in duodenum

Question 57

What are the actions of CCK (3)?

Answer 57

Stimulate secretion of pancreatic enzymes and potentiates secretin action Contraction of gall bladder Causes satiety by signalling on vagal afferent terminals

Question 58

Which enzyme can potentiate secretin?

Answer 58

CCK

Question 59

Which hormone stimulates gall bladder contraction and pancreatic enzyme secretion?

Answer 59

CCK

Question 60

Which enzyme stimulates HCO3- excretion?

Answer 60

Secretin

Question 61

What hormone stimulates pepsin and gastric acid secretion?

Answer 61

Gastrin

Question 62

What releases GLP1?

Answer 62

L cells in small intestine

Question 63

When is GLP1 released?

Answer 63

Meals, carbs, fat and GIP

Question 64

What does GLP1 do?

Answer 64

Potentiates glucose stimulated insulin release (sensitises beta cells to glucose) Suppresses appetite

Question 65

What secrets GIP?

Answer 65

K cells small intestine

Question 66

What does GIP do?

Answer 66

Potentiates glucose stimulates insulin release

Question 67

What stimulates GIP production?

Answer 67

Oral, glucose, fat and protein

Question 68

What hormone is important in gall bladder contraction?

Answer 68

CCK

Question 69

What hormone is important in pancreatic enzyme secretion?

Answer 69

CCK

Question 70

Where is CCK secreted from?

Answer 70

Duodenum

Question 71

What is CCK secreted in response to?

Answer 71

Chyme in duodenum