week 1

Question 1

explain the process of gastric acid secretion

Answer 1

vagus nerve releases ACh which acts on g cells and parietal cells
g cells release gastrin and parietal cells release HCl
gastrin stiulates ECL cells for histamine and parietal cells for HCl (CCK2 receptors)
histamine acts on parietal cells via H2 receptor and on d cells via H3 receptor for somatostatin
somatostatin inhibits parietal and ECL cells

Question 2

pathophysiology of peptic ulcer disease

Answer 2

imbalance between gastric acid secretion and mucous production
H.pylori produces urease which reacts with urea to produce ammonia
pH raised and so glands produce more acid
inflammation and ulceration
NSAIDs inhibit COX production and prevent mucous production making ulceration possible

Question 3

migrating motor complex

Answer 3

4 phases
1 - prolonged period of quiescence
2 - increased frequency of contractility
3 - a few minutes of peak electrical and mechanical activity
4 - declining activity merging to next phase 1
regulated by motilin - stimulates contraction of gastric fundus
cleanses stomach and intestine

Question 4

the function of interstitial cells of cajal

Answer 4

have a pacemaker function and lie in myenteric plexus
basic electrical rhythm of the gut determines how often an area of the gut can contract
variations in BER determine directionality - higher BER in proximal intestine than in distal

Question 5

treatment of peptic ulcer disease

Answer 5

antacids
sucralfates form a viscous suspension in presence of an acid. high affinity for damaged mucosa so provides a physical barrier over damaged mucosa
alginates form a gel-like raft that adheres to the top of the acid ‘pocket’ in the proximal stomach. release of CO2 makes gel float to proximal stomach creating a protective reflux barrier
H2 receptor antagonists
Protein pump inhibitors

Question 6

digestion of carbs in small intestine

Answer 6

pancreatic a-amylase breaks down a1-4 bonds in starch to form maltose, maltotriose, limit dextrin
broken down to glucose by maltase and isomaltase which are associated with epithelial cells of the intestinal wall
sucrose, lactose degraded by specific enzymes in brush border epithelia of the intestinal wall

Question 7

H2 receptor antagonists

Answer 7

cimetidine
ranitidine
famotidine

Question 8

fat digestion in small intestine

Answer 8

pancreatic lipase acts with bile to breakdown lipids
lipase degrades lips to monoacylglycerols, diacylglycerols and fatty acids - these promote lipid emulsification
emulsion particles are then coated by bile salts

Question 9

protein digestion in small intestine

Answer 9

digested by gastric pepsin and pancreatic/small intestinal endo and exo peptidases
trypsin breaks bonds adjacent to lysine and argine
chymotrypsin breaks bonds next to large hydrophobic residues - tryptophan, tyrosine, isoleucine
elastase breaks bonds adjacent to small hydrophobic residues - alanine and digests connective tissue