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Phys4 GI Lect5
Phys4 GI Motility II
Question | Answer |
---|---|
Small intestine motility in the FED state | Combination of Mixing and Paristalsis. **Mixing outweighs the short paristalsis. |
Small intestine motility in the FASTED state (2-3hrs after a meal) | 1.Few or no contractions. 2.MMC (Moves from mid stomach down to terminal ileum. It cycles every 90 minutes during the fasted state. Initiated by motilin and terminated by food in the stomach) |
3 things that can terminate MMC | 1.Food in stomach (mediated by hormones). 2.IV of gastrin & CCK. 3.Vagus neural impulses. |
Do slow waves themselves cause contractions? | NO, the spike potentials on top of them do. |
Peristaltic Reflex in the Small Intestine | "Law of intestine" not important in healthy people. Can sweep the entire length of the small Intestine. |
Intestino-Intestinal Reflex in the Small Intestine | Occurs when an area of bowel becomes grossly distended. SNS reflex causes contractile inhibition on the rest of the bowel (STOP). |
Power Propulsion | Long, large contractions in response to noxious stimuli. **Responsible for retrograde Vomitting AND orthograde explosive diarrhea. |
Gastro-Ileal reflex in the Intestine | Initiated by food in stomach (CCK, gastrin, extrenic), causes the opening of Ileo-cecal sphincter and contraction of ileum. **Making room for incoming food. |
Ileal Break | Inhibition of gastric and pancreatic secretion and motility in response to large infusion of lipids & carbs (sufficient enough to cause malabsorption). |
Effects of Ileal distention on Ileo-cecal sphincter? Colonic distention? | Ileal distention causes RELAXATION. Colonic distention causes CONTRACTION (b/c colon is loaded with bacteria and dont want that in small intestine). **Reflex mediate by Enteric NS. |
2 types of movement seen in Large Intestine | 1.Haustral Shuttling: Like mixing, Haustra will be visible. 2.Mass movements: (3-5 per day) Propulsion of contents towards rectum, Haustra DISAPPEAR. |
Gastrocholic Refelx in Large Intestine | Food in stomach (stretch) increases motility & mass movement in the Large intestine. **CCK, Gastrin, PNS. |
Enteric NS is mostly _______ in the large Intestine | INHIBITORY |
Rectosphincter reflex (Recto-anal reflex) | 1.Distention in the rectum causes passive Inc in pressure. 2.Leads to active contraction, fruther Inc pressure. 3.This relaxes the Int anal sphincter and contracts Ext anal sphincter. 4.Pressure builds at Ext spincter. 5.Pressure Rec adapt |
What determines contents within the anal canal? | Receptors within the anal canal determine whether its solid, liquid, or gas. |
Total transit time through the colon | 20-30hrs. Most labeled feces gone within 24hrs after entry into the colon. |
Continence Requirements | 1.Contraction of puborectalis. 2.Maintenance of anorectal angle. 3.Normal rectal sensation. 4.Contraction of the Ext anal sphincter |
Defecation requirements | 1.Relaxation of puboreactalis. 2.Straightening of anorectal angle. 3.Relaxation of sphincter. |