H20, Electrolytes and GI Motlility - Prunuske Flashcards
What is anismus?
Failure of normal relaxation of pelvic floor muscles and external anal sphincter in defecation
What is tenesmus?
Feeling that you need to pass stool, even when bowels are empty
What is ileus?
The disruption of the normal propulsive ability of the gastrointestinal tract
(NOT for reason of an obstruction)
3 things that modify claudins?
Go!
Wait… why would we want to modify claudins?
Tight junction permeability depends on claudins! 3 ways to modify claudins: 1) Cytokines 2) Bacterial Toxins 3) Hormones
Modifying claudins is a big part of fluid movement control!
Cells at the tips of the villi _______ fluid, whereas cells in the crypts of the villi ______ fluid.
Cells at the tips of the villi absorb fluid as it follows Na and nutrients, whereas cells in the crypts of the villi secrete fluid following Cl ions.
These two things can actually occur simultaneously!
I’m not really understanding the difference between electroneutral and electrogenic fluid uptake in the intestine….
Explain por favor!
Electroneutral: Na/H exchanger and Cl/HCO3 exchanger on apical side. Water follows. Powered by Na/K ATPase.
Electrogenic: Na and glucose uptake drives fluid absorption into intestine. No active transport of counter-ion, Cl- just passes through tight junctions and water follows
Ca can pass both intracellularly or paracellularly from the lumen into the blood.
What is the mechanism by which Ca passes through the cell intracellularly?
Ca channel on the apical brush border brings Ca inside when there is a gradient.
Three different basolateral mechanisms pull Ca into the blood and establish the Ca gradient.
1) Ca-ATPase
2) Ca/Na Exchanger
3) Exocytosis
Only 3-6% of ingested iron is absorbed. Where in the Gi tract is it mostly absorbed?
The duodenum!
You are recently diagnosed with a VIP-stimulating tumor. How are you now feeling about that cross-country Greyhound bus tour you were looking forward to?
You should be feeling anxious. A VIP-stimulating tumor will elevate cAMP. This will stimulate the CFTR channel to release Chloride into the intestinal lumen and water will follow. Basically you are going to have secretory diarrhea and are not going to want to be in a bus for days…
How does Linactolide treat constipation?
It activates GC-C receptors where Guanylin binds. Binding at this site creates more cGMP which willa ctivate CFTR channels. CFTR releases Cl and water will follow!
Watch out for E.Coli toxin that works in the same way, DIARRHEA CITY! Too much?
Uptake of what ion, through what channel, is central to stool dessication?
Na ion, through ENaC channels
Interesting that, ENaC channels also found in renal collecting ducts. So after low salt diet, ENaC will increase in expression due to aldosterone action. More Na is removed from stool.
In a normal and healthy adult, assuming a normal diet about 8 L of fluid is presented to the intestine every day. The reabsorption of the bulk of this fluid in the small intestine is primaryily driven by what?????
Nutrient-coupled electrogenic sodium absorption
BAM!
What kind of diarrhea is caused by excess secretion of Cl and inhibition of NaCl transport?
Secretory Diarrhea
Inflammation or Infection
What kind of diarrhea is caused by poor absorption of luminal substances?
Osmotic diarrhea
(water is pulled from the bloodstream by osmosis
How often does mass peristalsis promote rapid forward propulsion in the small bowel?
1-3 times per day.
How does distention of the ileum and distention of the cecum affect the tone of the iliocecal sphincter?
Ileal distension = relax sphincter
Cecal distension = contract sphincter
The Intestinointestinal Reflex causes the entire bowel to relax. When stimulates this reflex?
Stimulated by over-distension or traumatization - often due to surgery
What is the name of the reflex causes by distension of the ileum, resulting in decreases gastric motility?
Ileal-gastric reflex
This is a long reflex involving the vagus nerve
What is the gastro-ileal reflex?
Increased gastric activity causes:
- ileal contractions
- relaxation of the cecum
- relaxation of iliocecal sphincter
5-HT and ACh are important mediators in theis reflex which causes the urge to defecate after filling up the stomach:
Gastro-colic reflex
How do emotions affect the large intestine?
Increased sympathetic activity with epinephrine will DECREASE colonic motility
Increased parasympathetic activity with ACh will INCREASE colonic motility
What nerves control the external anal sphincter?
Somatic pudendal nerves
2 big causes behind irritable bowel syndrome?
Crohn’s Disease
Ulcerative Colitis
