🍔 3. Hormonal Control of Gastrointestinal Motility

• What are gastrointestinal hormones released into?

  Portal circulation
• What do gastrointestinal hormones exert actions on?

  Target cells with specific receptors
• What happens to the effects of hormones after severing nervous connections?

  Effects persist despite severed connections
• How do hormones affect motility compared to secretion?

  Motility effects are usually less important
• What cells secrete gastrin?

  G cells of the antrum
• What stimulates the secretion of gastrin?

  Ingestion-related stimuli like stomach distention
• What are the primary actions of gastrin?

  Stimulates gastric acid secretion and mucosal growth
• What cells secrete cholecystokinin (CCK)?

  I cells in the duodenum and jejunum
• What stimulates the secretion of CCK?

  Digestive products of fat and fatty acids
• What is the primary action of CCK on the gallbladder?

  Contracts gallbladder to expel bile
• How does CCK affect stomach contraction?

  Inhibits stomach contraction moderately
• How does CCK affect appetite?

  Inhibits appetite to prevent overeating
• What cells secrete secretin?

  S cells in the duodenum
• What stimulates the secretion of secretin?

  Acidic gastric juice entering the duodenum
• What is the effect of secretin on pancreatic secretion?

  Promotes secretion of bicarbonate
• What is the effect of secretin on gastrointestinal motility?

  Mild effect on motility
• What is another name for glucose-dependent insulinotropic peptide (GIP)?

  Gastric inhibitory peptide
• What stimulates the secretion of GIP?

  Fatty acids and amino acids
• What is the effect of GIP on gastric motility?

  Decreases motor activity of the stomach
• What does GIP stimulate at low blood levels?

  Stimulates insulin secretion
• What is the function of motilin?

  Increases gastrointestinal motility
• When is motilin secreted?

  During fasting
• What are the waves of gastrointestinal motility stimulated by motilin called?

  Interdigestive myoelectric complexes
• How often do interdigestive myoelectric complexes occur?

  Every 90 minutes during fasting
• What inhibits motilin secretion after food ingestion?

  Mechanisms not fully understood