Monogastric pt 2 Flashcards
What is a gut hormone?
- Must be secreted by gut cell and exert effect on another cell
- Endocrine route
- Stimulated by food
- Not dependent on neural control
- Synthetic form must mimic the actions of the native substance
What produces gastrin and what is the release stimulus?
G cells, duodenum. Peptides and aa
What does gastrin do?
Positive action on parietal cell and HCl secretion
What produces secretin and what is the release stimulus?
Duodenal S cells, jejunum; Acid, fat, and protein
What does secretin do?
Positive effect on HCO3 secretion negative effect on HCl secretion
What produces CCK and what is the release stimulus?
I cells, small intestine and enteric neurons; Fats protein
What is the effect of CCK
Positive effect on pancreatic enzyme and insulin secretion, positive effect on bile secretion, satiety factor
What produces GIP and what is the release stimulus?
K cells, duodenum and jejunum; Fats and glucose
What does GIP do?
Negative effect on gastric secretion and increase insulin secretion
What produces motilin and what is the release stimulus?
M cells, duodenum and jejunum; Duodenal pH increase and acetylcholine
What does motilin do?
Antral and duodenal MMC, Phase III induction during digestion
What are substances that signal via paracrine?
- Somatostatin
- Peptide YY
- Serotonin
- Histamine
What secretes serotonin?
Enterochromaffin cells
What does serotonin do?
- Stimulate enteric nervous system
- Vagal afferents (gut to brain)
- Enterocyte secretion
- Blood flow
What are the two paracrine effects of serotonin?
Enterochromaffin cells pick up hyperosmolality and acidity. Can either:
- Bind to receptors on sensory afferents
- Receptors on enterocytes
What drug blocks serotonin receptors and prevents nasaue?
Ondansetron
What increases the secretion of trophic factors?
Increase feed, increases demand, increases production and secretion of trophic factors
What promotes growth on the gastric mucosa?
Gastrin
What promotes growth of the intestinal mucosa?
CCK and enteroglucagon
What happens to regulatory peptides in cold adaptation?
Increased nutrition for warmth and therefore increased food intake. This increases the regulatory peptides and elongates intestinal villi leading to enhanced absorption
Muscle layers of the gut wall facilitate what?
- Propulsion
- Retention
- Physical breakdown of food
- Particle mixing and circulation
What is the propulsive movement?
Relationship to transit time/rate (dp/dt)
What is a syncytium?
Group of cells in which the protoplasm of one cell is continuous with that adjoining cells
What facilitates the protoplasmic continuity between smooth cells?
Gap junctions
What is a a gap junction?
2 Connexon. Used for exchange of substances between cells
Why are gap junctions so important in propulsion?
- protoplasmic continuity
- Low resistance pathway for ions to move
- Membrane potential changes are coordinated and waves move oral to aboral
Do slow waves always result in smooth muscle contraction?
No
Slow waves are…
Myogenic. no neural input needed
