Gut hormones

Question 1

two types of hormonal secretions

Answer 1

endocrine and paracrine

Question 2

endocrine secretions definition + key example

Answer 2

peptides synthesised by cells in the mucosa

gastrin

Question 3

paracrine secretions definition + key example

Answer 3

mainly regulatory peptides released from specialised cells found along the GI tract

histamine

Question 4

secretion of mucus stages

Answer 4

1. secreted by surface lining cells and mucous neck cells within the mucosa
2. secreted alongside bicarbonate to produce a pH gradient from the lumen to he mucosal surface

Question 5

what stimulates bicarbonate and mucous production?

Answer 5

prostaglandins

Question 6

what are prostaglandins an example of?

Answer 6

eiconasoids

Question 7

eiconasoid definition

Answer 7

signalling molecules made by enzymatic or non-enzymatic oxidation of arachidonic acid or other polyunsaturate fatty acids

Question 8

eiconasoid functions

Answer 8

mounting/inhibiting inflammation, allergy, fever and other immune responses

regulate abortion or pregnancy, normal child birth

perception of pain

regulate cell growth, blood pressure

Question 9

different types of eiconasoid

Answer 9

prostaglandins, thromboxanes, leukotrienes, prostacyclin

Question 10

prostacyclin function

Answer 10

prevents formation of platelet plug

vasodilator

Question 11

prostaglandin function

Answer 11

contraction of uterus

Question 12

aspirin function

Answer 12

inactivates COX preventing the conversion of arachidonic acid to prostaglandins and thromboxane

relieves pain

Question 13

aspirin side effect

Answer 13

reduces mucous production which increases risk of peptic ulcers

Question 14

gut hormones definition

Answer 14

group of hormones secreted by the enteroendocrine cells in the stomach, pancreas and small intestine that control various functions of digestive organs

Question 15

two main groups of GI hormone

Answer 15

gastrin like and secretin like

Question 16

gastrin like hormones definition + examples

Answer 16

gastrin and CCK which are structurally and functionally related

important hormonal regulators that are known to increase gastric secretion, stimulate pancreatic secretion and increased blood circulation

Question 17

where is gastrin produced?

Answer 17

gastric antrum, released from G cells

Question 18

what stimulates the release of gastrin + why?

Answer 18

protein digestion products- tryptophan- acid needs to be secreted to activate pepsinogen

submucosal plexus detects distention, leading to vagus nerve activation by release of ACh

Question 19

gastrin 2 actions

Answer 19

acid secretion, pepsin release

Question 20

gastrin acid secretion stages

Answer 20

1. binds to CCKb Gq coupled receptors
2. IP3- more calcium, triggers insertion of hydrogen potassium pump
3. stimulate ECL to secrete histamine which then acts on parietal cells

Question 21

what secretes pepsinogen?

Answer 21

chief cells of gastric glands located in the body and fundus of the stomach

Question 22

how are the peptide hormones released?

Answer 22

exocytosis of vesicles

Question 23

pepsinogen secretion stages

Answer 23

1. gastrin binds to M3 Gq coupled CCKa receptors

2. increase in IP3 and calcium leading to exocytosis of vesicles

Question 24

how else may pepsinogen be secreted?

Answer 24

chief cells have B2 receptors and secretin/VIP receptors that are cAMP mediated- increased phosphorylation leading to release of pepsinogen

Question 25

two triggers for histamine release

Answer 25

respond to stretch and vagal stimulation

Question 26

where is histamine released?

Answer 26

ECL cells in body of the stomach

Question 27

CCK synonyms

Answer 27

cholecystokinin, pancreozymin

Question 28

where is CCK produced?

Answer 28

I cells of the duodenum and jejunum

Question 29

what stimulates CCk secretion? why?

Answer 29

chyme in duodenum, especially high in fats and protein digestion products

lead to the contraction of the gall bladder to secrete bile and release of pancreatic enzymes and buffers to better digest the fats and proteins

Question 30

explain action of CCK

Answer 30

binds to CCKb and a receptors on acinar cells of pancreas and smooth muscle of gall bladder

Gq coupled receptors, increased calcium which triggers contraction and secretion

Question 31

secretin like hormones definition and examples

Answer 31

polypeptidic hormones that are structurally related

glucagon, GIP, VIP and secretin

Question 32

where is secretin produced?

Answer 32

S cells of the duodenum, located in the intestinal glands

Question 33

what is the trigger for secretin release?

Answer 33

low duodenal pH due to too much HCL in chyme

increased by protein digestion products in the mucosa of the duodenum (showing that the protein has already been digested)

Question 34

secretin functions

Answer 34

neutralise pH in the duodenum

modulates water and electrolyte transport

Question 35

secretin mechanism of action

Answer 35

1. binds to secretin receptors on pancreatic acinar cells
2. Gs receptors, convert ATP to cAMP
3. leads to the secretion of bicarbonate rich fluid

Question 36

physiological events during cephalic phase

Answer 36

vagal stimulation leading to GRP and ACh release

increased acid secretion from parietal cells

more histamine release

ACh inhibits D cells and reduces somatostatin

Question 37

physiological events during gastric phase

Answer 37

distention of gastric mucosa activates vagal afferent pathway - leading to secretion of ACh - more acid in stomach

protein digestion products stimulate G cells - more acid

more gastrin more pepsinogen

pH too low- stimulates secretin

Question 38

physiological events during intestinal stage

Answer 38

protein and lipid digestion products stimulate secretion of CCK