Gut Motility Flashcards
What controls the enteric nervous system?
Interstitial cells of Cajal. These have intrinsic pacemaker activity and play a role in neural control in the gut. They are found in the myenteric plexus.
List the 4 stages to the migratory motor complex.
Phase I: Prolonged period of quiescence
Phase II: Increased frequency of contractility
Phase III: A few minutes of peak electrical and mechanical activity
Phase IV: Declining activity merging to next phase I.
What hormone regulates the migratory motor complex?
Motilin.
What action does erythromycin have on the gut?
Erythromycin is also a motilin agonist hence why people sometimes get diarrhoea with this antibiotic.
What does motilin do?
Motilin is released from M cells in the small intestine at 90 minute intervals. It is known as the “housekeeper” of the gut because it cleanses the gut in time for the next meal. It stimulates contraction of the gastric fundus and enhances gastric emptying.
What treatments would you use in cases of gastroparesis (delayed gastric emptying)?
5-HT4 agonists - Cisapride - Metoclopramide D2 antagonists - Metoclopramide - Domperidonem Motilin Agonist - Erythromycin Botulinum toxin injection into pyloric sphincter to relax it (temporary).
What causes Ogilvie’s disease?
Otherwise known as acute colonic pseudo-obstruction, it is caused by large bowel parasympathetic dysfunction. It is common after cardio-thoracic or spinal injury and there is a risk of cecal perforation.
Name some conditions associated with chronic intestinal pseudo-obstruction
Scleroderma, Amyloidosis, Parkinson’s Disease, Diabetes Mellitus, Severe Hypothyroidism, Use of Phenothiazines, Use of Anti-Parkinsons drugs
What is the action of Loperamide?
A gut selective opiate Mu receptor agonist. It is the only drug purposely used to affect motility. It decreases tone and activity of the myenteric plexus. It also slows colonic transit leading to increased water absorption and is used in the symptomatic management of diarrhoea.
What is Prucalopride?
5-HT4 receptor agonist. Used in patients with chronic constipation that have failed on at least 2 laxatives.
What is Linaclotide?
Minimally absorbed guanylate C receptor agonist. Increases the secretion of chloride and HCO3 into the lumen and thus increases intestinal fluid and speeds colonic transit. It is licensed for treatment of IBS.
Why are prucalopride and linaclotide better than laxatives?
Because they regulate bowel movements and don’t make you go at inconvenient times.
What happens in obstructive defecation?
There is paradoxical contraction of the puborectalsis and external anal sphincter during defecation.
What is Hirschrung’s Disease?
It is a failure of development of the nervous system in the rectosigmoid and sometimes the whole colon, whereby nerve cells fail to migrate. As a consequence of that they have no activity and they get constipation. It must be considered if a child hasn’t opened their bowels very soon after birth.
