Gastric Physiology 4/12/23

Question 1

4 Key cell types in Stomach

Answer 1

Mucous
Parietal
Chief cells
Enterendocrine cells

Question 2

What cells secrete Gastric acid?

Answer 2

Parietal cells

Question 3

What type of acid is Gastric acid?

Answer 3

Hydrochloric acid

Question 4

How are H+ ions taken out of Parietal cells?

Answer 4

Via active transport

Question 5

What type of stimulation turns on Gastric acid secretion in the Cephalic stage?

Answer 5

Parasympathetic

Question 6

Which Neurotransmitter is released during Stimulation of Gastric acid secretin during the cephalic phase?

Answer 6

Acetylcholine

Question 7

What causes the Cephalic phase of Gastric acid secretion to begin?

Answer 7

Sight, Smell and taste of food
Chewing

Question 8

What two things does Acetylcholine do in the cephalic phase?

Answer 8

Acts directly on parietal cells
ACh triggers release of gastrin and histamine

Question 9

Second phase of Gastric acid secretion name?

Answer 9

Gastric phase

Question 10

How much HCl does the average human produce per day

Answer 10

2 litres/day

Question 11

What is released during the Gastric phase?

Answer 11

Gastrin

Question 12

What does the release of Gastrin trigger to be released?

Answer 12

Histamine

Question 13

What does Protein in the stomach trigger the release of?

Answer 13

Gastrin

Question 14

How does increased proteins in the Lumen cause more parietal cell activity?

Answer 14

Acts as a buffer, mops up H+ ions
Decreases secretion of somatostatin

Question 15

What is Somatostatin?

Answer 15

Protein that reduces Gastrin secretion

Question 16

What causes Gastric acid secretion to turn off in the Gastric Phase?

Answer 16

Low luminal pH

Question 17

What causes gastric acid secretion to turn off in the intestinal phase (4)

Answer 17

Duodenal distension
Low luminal pH
Presence of Amino acids and fatty acids

Question 18

What is released in the intestinal phase?

Answer 18

Enterogastrones

Question 19

Two enterogastrones released in Gastric acid secretion? What do they do?

Answer 19

Secretin (Inhibits gastrin release promotes somatostatin release)
Cholecystokinin (CCK)

Question 20

Summary of Gastric acid release:
Name for 1 Neurotransmitter
Name for 1 hormone
Name for 2 Paracrine factors
Name for 2 Entetrogastrones

Answer 20

ACH
Gastrin
Histamine + somatostatin
Secretin + CCK

Question 21

What is an Ulcer?

Answer 21

Breach of a mucousal surface

Question 22

Causes of Peptic ulcers (4)

Answer 22

Helicobacter Pylori
Drugs (NSAIDS)
Chemical irritants- alcohol, bile salts and dietary factors
Gastrinoma

Question 23

4 Ways Gastric Mucosa defends itself?

Answer 23

Alkaline Mucus
Tight junctions
Replacement of damaged cells
Feedback loops

Question 24

How does Helicobacter pylori cause reduced mucosal defence?

Answer 24

Splits urea into CO2+ Ammonia
Produces Ammonium
Ammonium secretes proteases and phospholipases which damage gastric epithelium

Question 25

What does NSAIDs stand for?

Answer 25

Non-Steroidal anti inflammatory drugs

Question 26

What do NSAIDs inhibit? What does this do?

Answer 26

Inhibits cyclo-oxygenase 1 Reduces mucosal defence

Question 27

What do Bile salts do to mucosal layer?

Answer 27

Strip it away Reducing mucosal defence

Question 28

What is the therapy called for Helicobacter pylori?

Answer 28

Triple Therapy consists of 1 proton pump inhibitor and 2 antibiotics

Question 29

Examples of 3 proton pump inhibitors?

Answer 29

Omeprazole Lansoprazole Esomeprazole

Question 30

H2 Histamine receptor antagonist two examples?

Answer 30

Cimetidine Ranitidine

Question 31

What do Chief cells produce in the Stomach? Which is the inactive form of?

Answer 31

Pepsinogen Pepsin

Question 32

What nervous system mediates pepsinogen release? What neurotransmitter is involved?

Answer 32

Enteric nervous system Acetylcholine

Question 33

What is Pepsin? What else stimulates the conversion of Pepsinogen --> pepsin?

Answer 33

Protease HCl

Question 34

What pH is the conversion of pepsinogen to pepsin most effective?

Answer 34

pH<2

Question 35

What protease stimulates the conversion of pepsinogen-pepsin? What is this process called?

Answer 35

Pepsin Positive feedback loop

Question 36

What causes the irreversible inactivation of pepsin? Where?

Answer 36

HCO3- Small intestine

Question 37

Is Pepsin essential? What percentage of total protein digestion does it account for?

Answer 37

Not essential app 20% of total protein digestion

Question 38

What is Empty stomach volume What is the Maximum stomach capacity?

Answer 38

Empty~50mL Eating~1.5L

Question 39

What mediates Receptive relaxation in the Stomach?: Nervous system Nerve(1) Neurotransmitters (2)

Answer 39

Parasympathetic (Enteric nerve plexuses) Vagus nerve Nitric oxide and Serotonin

Question 40

Part of stomach where most powerful contraction during peristalsis occurs?

Answer 40

Gastric antrum

Question 41

What determines the frequency of peristaltic waves and where is it? Average frequency of Electrical rhythms?

Answer 41

Pacemaker in Muscularis propria 3/minute

Question 42

Strength of peristaltic contractions increased by what two factors?

Answer 42

Gastrin Gastric distension

Question 43

What 5 factors is the Strength of peristaltic contractions decreased by?

Answer 43

Increased duodenal luminal fat Increased Duodenal osmolarity Decreased Luminal pH Increased Sympathetic NS action Decreased Parasympathetic NS action

Question 44

What is Gastroparesis

Answer 44

Delayed gastric emptying