GIT Regulation

Question 1

Neurocrine Regulation

Answer 1

• Peptides released by nerves within gut
• Short-range effects
• Includes: ACh (SM contraction), Substance P (SM contraction), NE (SM relaxation), Vasoactive Intestinal Peptide (SM relaxation)

Question 2

Endocrine/Hormonal Regulation

Answer 2

• Hormones synthesized by cells in Gastric & Intestinal epithelium & released into blood stream
• Systemic long-ranged action
• Includes: Gastrin, Secretin, CCK, Incretins (GIP & GLP)

Question 3

Paracrine Regulation

Answer 3

• Substances that act locally within same tissue
• Short-range effects
• Includes: Histamine, Somatostatin

Question 4

Gastrin

Answer 4

• Endocrine/hormone regulator
• Secretion: from Gastric Antrum after meal
• “Gatrin keeps you thin” - satiety
• Stimulus for release: Stomach distention, Vagal stimulation, small polypeptides & AAs (Phe & Trp)
• Inhibition: H+ (acidity) in stomach lumen
• Effects: Increase H+ secretion, Stimulate Gastric Mucosa growth

Question 5

Cholecystokinin (CCK)

Answer 5

• Homologous to Gastrin
• Effects: Gallbladder contraction & Bile secretion, Pancreatic enzyme secretion, inhibits Gastric emptying - more time for intestinal digestion & absorption
• Stimulus for release: Small peptides/AAs, FAs/Monoglycerides

Question 6

Secretin

Answer 6

• Endocrine regulator
• Homologous to Glucose
• Effects: Reduce acidity in Small Intestine, Pancreatic HCO3- secretion/neutralaize H+ in lumen, Increase bile production, Stimulate HCO3- & H2O secretion by Liver
• Inhibition: H+ secretion by Gastric Parietal Cells

Question 7

Incretins

Answer 7

• Enhance Insulin secretion in response to oral carbs - anticipatory response
• Includes: Gastric Inhibitory Peptide (GIP) & Gastric Like Peptide (GLP1)
• Inhibition: H+ secretion by Gastric Parietal Cells - limit stomahc acidifciation

Question 8

Somatostatin

Answer 8

• Paracrine regulator
• Inhibition: Via Vagal Stimulation, inhibits release of GI hormones & H+ secretion
• Secretion: Response to luminal H+

Question 9

Histamine

Answer 9

• Paracrine regualtion
• Secretion: Via mast cells of gastric mucosa
• Effects: Increases Gastric H+ secretion directly & potentiates effects of Gastrin & Vagal stimulation