Fluid and Electrolytes Flashcards
What is the target of the C.diff toxin A and B?
Cytoskeleton disruption
What is absorbed and secreted in the large intestines?
HCO3 and K are secreted
Na, Cl, and H2O are absorbed
How is Na absorbed in the intestines? (3)
SLGT1, amino acid B transporters, and Na?h exchanger during the fed state with paired Na/K pump on the basolateral side
What ion always goes with HCO3?
Cl–always in opposite directions
What causes Cl absorption?
Na absorbed, so Cl pulled along, as well as a HCO3/Cl exchanger
What is the protein that regulates Cl/water secretion? What ion (not Cl) is needed for it to function?
CFTR (cystic fibrosis transport regulator)–need Ca, cAMP
How is K secreted from the large intestines?
Net negative lumen of the intestines, as well as Na/K pump
How is K reabsorbed in the small intestines?
Follows water back in the intestines between the cells
What is the function of increased cAMP, cGMP, and Ca in the intestinal lumen? (2) What is the net effect of this?
Inhibits Na/H pump, increases Cl channel
Thus Na remains in the lumen, and Cl is secreted into the lumen
Somatostatin always has what effect on the GI system (inhibitory or excitatory)?
generally inhibitory, but promotes fluid absorption
What are the four causes of diarrhea?
- Increased intestinal secretion
- Decreased intestinal absorption
- Increased osmotic load
- Abnormal intestinal motility
What is osmotic diarrhea?
Diarrhea caused by a nonabsorbable nutrient
What is secretory diarrhea?
Diarrhea caused by intestinal secretion of fluid and electrolytes
Osmotic, secretory, or both: disaccharidase deficiency?
Osmotic
Osmotic, secretory, or both: enterotoxins?
Secretory
Osmotic, secretory, or both: inflammatory cytokines
Both
Osmotic, secretory, or both: pancreatic enzyme deficiency
Osmotic
Osmotic, secretory, or both: Nutrient-binding substances
Osmotic
Osmotic, secretory, or both: tumor (VIP, 5HT secretion)?
Secretory
Osmotic, secretory, or both: infectious disease?
Both
Osmotic, secretory, or both: bacterial overgrowth?
Osmotic (think biofilm)
Osmotic, secretory, or both: antacids
Osmotic
Osmotic, secretory, or both: loss of electrolytes
Osmotic
What is the primary cause of diarrhea in celiac?
Increased oncotic pressure of the intestines d/t a lack of uptake–thus it is a osmotic diarrhea
What is the effect of PPIs on intestinal microbiota?
pH increased, thus lost host defense
What is the effect of antidiarrheal agents on c.diff infections?
Lowers intestinal motility, and thus makes matters worse
True or false: pseudomembranes with C.diff = biofilm
False–it is immune cells, bacteria, and debris
What are the three ways in which you can increase second messenger generation in the intestinal epithelial cells?
Neuronal
Paracrine
Bacterial toxins
What are the two endocrine regulators of the intestinal epithelium that can be upregulated via transcriptional regulation, and cause an increase in Na-K channels?
Mineralocorticoids
Glucocorticoids
What is the effect of somatostatin on fluid absorption? How?
Increases by increasing the Na-H exchanger
What are the three neuronal neurotransmitters that increase second messenger generation in the intestines? What does this do?
Ach
VIP 5HT
Stimulates CFTR, inhibits Na-H exchanger
What are the two paracrine regulators of the intestinal epithelium that generate second messengers? What is the effect of this?
Prostaglandins
Histamine
Stimulates CFTR, inhibits Na-H exchanger
What is the MOA of second messenger generation on fluid absorption vs secretion?
Increases secretion by increasing activity of CFTR, and inhibiting Na-H exchanger
What is the MOA of glucocorticoids/mineralocorticoids on fluid uptake/secretion?
Increases absorption via upregulation of Na channels and Na-K ATPase
What is the effect of VIP and 5HT on intestinal secretion? How?
Increases by increasing second messenger generation (e.g. cAMP, cGMP, Ca)
What is the effect of exercise on GI motility?
Increases
What is the effect of fluid intake on GI motility?
Increases
What is the effect of anticholinergics on GI motility? How?
Decreases d/t decreased stimulation of Ach, which increases smooth muscle contraction
How can delayed gastric emptying cause diarrhea?
Inconsistent motility impairs digestive process
How does Gluten intolerance cause diarrhea?
Dramatic decrease of surface area leads to a decrease in fluid absorption. Thus osmotic diarrhea.
What is responsible for the secretory part of diarrhea caused by C.diff? Osmotic?
Secretion = Inflammation Osmotic = dead cells cause oncotic pressure
Does the large intestine participate in and significant nutrient absorption?
With the exception of water and electrolytes, no
Is K secreted or absorbed in the small intestines? Large?
Small = absorbed Large = secreted
What are the four key transport proteins involved in the reuptake of Na in the intestines?
- SLGT1
- AA transporter B
- Na-H exchanger
- Na channel
What is the transport protein on the basolateral side of the intestinal membrane needed for the four main transport protein to work?
Na/K pump
What are the two mechanisms for Cl absorption in the intestines?
- Passive diffusion following Na
2. Cl/HCO3 exchanger
What is the main protein involved in Cl secretion?
CFTR
What is the main way K is reabsorbed in the small intestines?
Via solvent drag with Na
What are the three secondary messengers that regulate CFTR and Na-H transporters? What effect do these have on the aforementioned transporters?
Ca, cAMP, cGMP
Increases CFTR
Inhibits Na-H
What is the MOA of inflammation causing diarrhea?
Death of epithelial cells = increased oncotic pressure, and decreased absorptive ability
