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Gastrointestinal > Gastric Physiology 4/12/23 > Flashcards

Gastric Physiology 4/12/23 Flashcards

1
Q

4 Key cell types in Stomach

A

Mucous
Parietal
Chief cells
Enterendocrine cells

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2
Q

What cells secrete Gastric acid?

A

Parietal cells

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3
Q

What type of acid is Gastric acid?

A

Hydrochloric acid

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4
Q

How are H+ ions taken out of Parietal cells?

A

Via active transport

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5
Q

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

A

Parasympathetic

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6
Q

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

A

Acetylcholine

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7
Q

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

A

Sight, Smell and taste of food
Chewing

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8
Q

What two things does Acetylcholine do in the cephalic phase?

A

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

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9
Q

Second phase of Gastric acid secretion name?

A

Gastric phase

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10
Q

How much HCl does the average human produce per day

A

2 litres/day

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11
Q

What is released during the Gastric phase?

A

Gastrin

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12
Q

What does the release of Gastrin trigger to be released?

A

Histamine

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13
Q

What does Protein in the stomach trigger the release of?

A

Gastrin

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14
Q

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

A

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

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15
Q

What is Somatostatin?

A

Protein that reduces Gastrin secretion

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16
Q

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

A

Low luminal pH

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17
Q

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

A

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

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18
Q

What is released in the intestinal phase?

A

Enterogastrones

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19
Q

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

A

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

20
Q

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

A

ACH
Gastrin
Histamine + somatostatin
Secretin + CCK

21
Q

What is an Ulcer?

A

Breach of a mucousal surface

22
Q

Causes of Peptic ulcers (4)

A

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

23
Q

4 Ways Gastric Mucosa defends itself?

A

Alkaline Mucus
Tight junctions
Replacement of damaged cells
Feedback loops

24
Q

How does Helicobacter pylori cause reduced mucosal defence?

A

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

25
Q

What does NSAIDs stand for?

A

Non-Steroidal anti inflammatory drugs

26
Q

What do NSAIDs inhibit? What does this do?

A

Inhibits cyclo-oxygenase 1
Reduces mucosal defence

27
Q

What do Bile salts do to mucosal layer?

A

Strip it away
Reducing mucosal defence

28
Q

What is the therapy called for Helicobacter pylori?

A

Triple Therapy
consists of 1 proton pump inhibitor and 2 antibiotics

29
Q

Examples of 3 proton pump inhibitors?

A

Omeprazole
Lansoprazole
Esomeprazole

30
Q

H2 Histamine receptor antagonist two examples?

A

Cimetidine
Ranitidine

31
Q

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

A

Pepsinogen
Pepsin

32
Q

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

A

Enteric nervous system
Acetylcholine

33
Q

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

A

Protease
HCl

34
Q

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

A

pH<2

35
Q

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

A

Pepsin
Positive feedback loop

36
Q

What causes the irreversible inactivation of pepsin?
Where?

A

HCO3-
Small intestine

37
Q

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

A

Not essential
app 20% of total protein digestion

38
Q

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

A

Empty~50mL
Eating~1.5L

39
Q

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

A

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

40
Q

Part of stomach where most powerful contraction during peristalsis occurs?

A

Gastric antrum

41
Q

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

A

Pacemaker in Muscularis propria
3/minute

42
Q

Strength of peristaltic contractions increased by what two factors?

A

Gastrin
Gastric distension

43
Q

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

A

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

44
Q

What is Gastroparesis

A

Delayed gastric emptying

45
Q
A

Gastrointestinal (6 decks)

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