Physiology and Pharmacology of Gastric Motility and Secretion Flashcards Preview

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Flashcards in Physiology and Pharmacology of Gastric Motility and Secretion Deck (54)
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1

What is stomach relaxation driven by?

vagus nerve

2

What is the starting point for digestion of proteins?

HCl and pepsin

3

What is produced by the stomach?

chyme

4

What are the rugae?

folds in the empty stomach

5

What is the fundus?

top of stomach, gas pocket, usually no food

6

What is the antrum?

next to duodenum - thick sm. muscle for contraction

7

How is food mixed in the stomach?

peristalic wave forces chyme down and back against pyloric sphincter which causes retropulsion

8

What size of food does the pyloric sphincter let through?

2mm or less

9

What governs the strength of the antral wave?

gastric factors and duodenal factors

10

What are the gastric factors mediating the antral wave?

rate of emptying is proportional to volume of chyme in stomach
distension increases motility due to stretch of smooth muscle, stimulation of intrinsic nerve plexus and increased vagal nerve activity and gastrin increase
consistency of chyme

11

What are the duodenal factors mediating the antral wave?

must be ready to recieve chyme and can delay emptying

12

How does the duodenum delay emptying of the stomach?

neuronal response - enterogastric reflex decreases antral peristalic wave from intrinsic nerve plexuses and ANS
hormonal response - release of secretin and CCK

13

What are the stimuli that drive the neuronal and hormonal responses of the duodenum?

fat - particularly potent as time required for digestion
acid - time needed for neutralisation by HCO3
hypertonicity - products of carbohydrate/ protein digestion are osmotically active and draw water into the sm. intestine
distension

14

Where do secretions from the gastric glands come from?

Pyloric Gland Area
Oxyntic Mucosa

15

What is produced by the oxyntic mucosa?

enterochromaffin cells - histamine - paracrine
chief cells - pepsinogen
parietal cell - HCl, Intrinsic factor

16

What is produced by the pyloric gland area?

D cell - somatostatin - endocrine
G cell - gastrin - endocrine

17

What is the function of HCl?

activates pepsinogen -> pepsin
denatures protein
kills most micro-organisms ingested

18

What is the function of pepsinogen?

inactive precursor of peptidase - pepsin
pepsin is autocatalytic once formed

19

What is the function of Intrinsic Factor?

binds vitB12 - allowing absorption in the terminal ileum - essential as only found in stomach

20

What is the function of histamine?

stimulates HCl secretion

21

What is the function of mucus?

protects stomach wall

22

What is the function of gastrin?

stimulates HCl secretions

23

What is the function somatostatin?

inhibits HCl secretion

24

What are the processes involved with secretion of HCl?

Conversion of CO2 and H20 to HCO3 + H
HCO3 exiting the cell and bringing Cl into the cell
H being extruded into the cannaliculus
Cl being extruded into the cannaliculus

25

What converts CO2 and H20 to H2CO3?

carbonic anhydrase

26

What takes HCO3 out of the cell?

HCO3/Cl antiporter

27

How is H taken into the cannaliculus?

via H-K ATPase

28

Which cell produces HCl?

The parietal cell

29

How is H+ increased by the parasympathetic nervous system?

ACh stimulates M3 on parietal cells and M1 on ECL cells
Gastrin activates CCK2Rs on parietal and ECL cells
Hitamine generated from M1 and CCK activates H2R on parietal

30

What inhibits the production of HCl?

somatostatin by inhibiting gastrin release
PGE2 inhibits all H2, M3 and CCK2 Receptors