Slides for every day from now until exams

Question 1

What is the stimulus, release from, function and inhibition of Gastrin?

Answer 1

• Stimulus: Peptides, AA’s. Distention, CN X
• Released from: G cells, stomach antrum
• Function: stimulate parietal cell H+ secretion and growth of the gastric mucosa
• Inhibited by: increasing acid secretion, somatostatin

Question 2

What is the stimulus, release from, function and inhibition of Somatostatin?

Answer 2

• Stimulus: decrease in stomach pH
• Released from: D cells in the gastric mucosa and in the pancreas
• Function: Inhibits parietal cells, inhibits gastrin release
• Inhibited by:

Question 3

What is the stimulus, release from, function and inhibition of CCK?

Answer 3

• Stimulus: Fats, small peptides and aa’s
• Released from: I cells jejunal mucosa
• Function: stimulates contraction of gall bladder, bile, hco3 and exocrine pancreas enzyme release into the git, inhibit stomach emptying, signals satiety
• Inhibited by: low luminal contents?

Question 4

What is the stimulus, release from, function and inhibition of GIP?

Answer 4

• Stimulus: Glucose, proteins, FAs in duodenum
• Released from: K cells duodenum
• Function: to stimulase insulin release and inhibit gastric acid secretion
• Inhibited by:

Question 5

What is the stimulus, release from, function and inhibition of Secretin?

Answer 5

• Stimulus: low luminal pH, FAs
• Released from: S cells duodenal mucosa
• Function: stimulates acinar cells of the pancreas to secrete HCO3 to neutralise stomach acid
• Inhibited by:

Question 6

Explain the role of stress in IBD

Answer 6

• Activation of the brain gut axis
• Increases cap permeability
• activation of mucosal mast cells
• flare up

Question 7

Outline how carbohydrates are absorbed in the digestive system

Answer 7

• broken down by salivery amylase
• broken down by pancreatic amylase
• Glu and Gal transported by Na co transporter (SGLT1)
• Fructose by facilitated diffusion SGLT5
• Fructose is then mainly converted into glucose and all are transported to blood by SGLT2

Question 8

Outline how Proteins are absorbed

Answer 8

• proteins broken down by pepsin in stomach
• further broken down by pancreatic enzymes
• AAs absorbed by Na+/AA co transporter
• Di- and tri- peptides transported by peptide/H+ co transporter
• Large transported by transcytosis

Question 9

outline the absorbtion of fats

Answer 9

• fats are coated in bile acids –> form mixed micelles
• allows for lipase to come in and act on exposed surface
• cleavage to form free fatty acids, glycerol monoglycerides and cholesterol

Question 10

Outline how bile acids are made and secreted

Answer 10

• Bile acids are conjugated with glycine or taurine
• Become bile salts (increased solubulity)
• Get secreted into the duodenum
• Deconjugated by gut flora
• Reabsorbed in enterohepatic circulation

Question 11

What things get conjugated with glucaronide?

Answer 11

• Billirubin gets conjugated with glucaronide —> bile —> metabolised by gut flora to urobilinogen and stercobilin —> stercobilinogen excreted in feces and urobilinogen reabsorbed and excreted in urine
• the oral contraceptive pill also gets conjugated with glucaronide to increase H2O solubility —> excreted via bile —> deconjugated by gut flora —> reabsorbed