Proteases, Gastric Motility/Emptying Flashcards
What molecule produced by chief cells is a precursor for pepsin?
Pepsinogen
Which cells in stomach produce pepsin?
None!
What is most ideal pH for conversion to pepsin? and what molecule is needed?
<2
HCl
What is role of pepsin in protein digestion?
1) Accelerates it
2) ~20% total protein digestion, where B.D collagen in meat
What is volume of empty stomach and max volume?
50mls
1.5L
What happens in receptive relaxation?
SMuscle in body and fundus relax before food arrives, so volume increases
Afferent input from Vagus nerve (NO and Serotonin can also have effect)
Where do peristaltic waves begin and where are they most powerful?
1) In the gastric body
2) In the gastric antrum
Why does PS close as peristaltic wave reaches it?
1) So little chyme enters duodenum
2) Gastric contents forced back and mix together in stomach body
What is the frequency of waves/min and what determines the frequency?
1) 3/minute
2) Interstitial Cells of Cajal
What 2 factors increase strength of peristaltic contractions?
1) Gastrin
2) Gastric Distension
What 5 factors decrease strength of peristaltic contractions?
1) Duodenal distension
2) Low pH in duodenum lumen
3) Increased duodenal osmolarity and luminal fat
4) Increased sympathetic action
5) Decreased Parasympathetic action
What do parietal cells secrete?
HCl and Intrinsic Factor
What is Gastroparesis?
Delayed gastric emptying
What is used to treat Gastroparesis?
(Drugs):
1) Gastrointestinal agents
2) Anticholinergic mediations
3) Miscellaneous e.g Levodopa
What does a high pH do?
Irreversibly inactivates pepsin
