2.09 Reflexes, Fluid, and Electrolyte Balance Flashcards
What is the basal state of stomach secretion?
low H+ secretion
circadian rhythm
lower between meals
What are the 3 phases of acid secretion?
cephalic
gastric
intestinal
Phase where 30% HCl secreted into gastric lumen prior to entry of food into stomach sensed by chemo/mechanoreceptors (stimuli) mediated by vagus nerve?
cephalic phase
What are the mechanisms at play for the cephalic phase?
vagus nerve
parietal cells
ECL cells
GRP - G cells
(inhibition) D cells-somatostatin
Phase where 60% Hcl secreted with food now in the stomach stimulated by distension and partially digested proteins (G cells)?
gastric phase
Gastric phase mechanism?
Local ENS reflex - ACh
Vagoavagal reflex
(Antral G cell + ECL)
ACh + GRP + Gastrin
Gastrin-Histamine Stim
What receptor does ACh attach to on the Antral G cell, ECL cell, and parietal cell respectively?
M3
Phase where 10% HCl secreted when food leaving the stomach and entering the intestine, the small intestine can signal the stomach to make more acid since it doesn’t have parietal cells?
Intestinal Phase
Mechanism for intestinal phase?
protein digestion products trigger
(G cell + endocrine cell + absorbed AA)
gastrin & “entero-oxyntin” to parietal cells
Nervous & Humoral
hormone
released by the duodenum in response
to acidic chyme entering from the
stomach
Secretin (from S cells)
Secretin will work to trigger what from the pancreas to help
neutralize the acid in the upper
duodenum?
bicarbonate
(HCO3-)
What generally excites pepsin and acid production?
parasympathetics
What CCK? What does it do?
From I cells @duodenum they allow pancreas,
gallbladder, stomach
Increase enzyme secretion, contracts
gallbladder, decreases gastric emptying
What is absorbed at the small intestine?
Water, Sodium, Chlorine, Potassium
What is secreted at the small intestine?
HCO3
How much of the 8.5L/day fluid load that reaches the small intestine is reabsorbed?
6.5L/day
What makes up the body fluid load that the small and large intestine work at reabsorbing?
food, saliva, secretions (gastric, pancreatic, bile, small intestine)
How much of the 2L/day fluid that reaches the colon reabsorbed? How much is excreted in feces?
1.9L/day reabsorbed
0.1L/day excreted
What is the max absorptive capacity of the colon?
4-6L/day
What is absorbed at the distal colon?
Water, Na, Cl
What is secreted at the distal colon?
K+ and HCO3
What happens if there is excess fluid at the colon?
diarrhea
What is required to maintain the Na+ driving force across the apical membrane?
Na+/K+ pump
What kind of absorption is dominant in the small intestine?
Na+ nutrient coupled (ex. glucose + AA)
An increased prevalence of what in the intestinal lumen can help enhance Na+ absorption?
glucose or amino acids
How does glucose stimulate more Na+ reabsorption at small intestine?
osmotic
gradients (cAMP independent)
What can you recommend that a mild dehydrated and acidotic patient with diarrhea take to replenish absorption?
oral rehydration solution (ORS)
(Glucose + electrolytes)
How does the small intestine and colon absorb Na+?
apical and basolateral membrane transport
processes (passive and active)
How does the small intestine and colon absorb Cl-?
apical and basolateral membrane transport
processes or paracellular/transcellular* (passive)
What are the ways that Cl- can be reabsorbed?
passive trans/paracell
Cl-HCO3 exchange
Na-H parallel
Where does the electrogenic Cl- secretion occur?
crypts of small and large intestine
What are the Cl- secretion mechanisms?
Na-K pump
Na/K/Cl cotransporter
2 types of K+ channels
What is the Cl- channel present at the apical membrane?
cystic fibrosis
transmembrane conductance
regulator [CFTR]
The net result of Cl- secretion is responsible for what?
secretion of NaCl
What parts of the GI are responsible for the dynamic K+ reabsorb/secrete balance?
small intestine
absorbing K+
distal intestine secreting K+
How does K+ absorption in small
intestine likely occurs?
solvent drag
How does passive K + secretion in
colon occurs?
lumen-negative
Vm via tight junctions
How is active K + secretion
mediated?
aldosterone
and cAMP
Where does active K+ secretion take place and what fuels it?
distal colon fueled by apical H-K pump
What are common Vitamin K food sources?
brussels sprouts, pork chops, avocadoes, broccoli, kale, spinach, liver, chicken, kiwi, prune, green beans and peas
