Electrolytes & Water Flashcards
list sources of enterosystemic fluids
list losses of enterosystemic fluids
is the absorptive capacity of the colon high?
YES
what provides reserve capacity for colon?
colonic fluid
ENaC
how does epithelium control enterosystemic fluid balance?
secretion - crypts of SI and LI
absorption - villi in SI
what is water transfer linked to?
chyme
Na
Cl
K
bicarb
SI is a net absorber of ____ and a net secretor of ___.
absorb - water, Na, Cl, K
secrete - bicarb
SI fluid absorption is ____.
isomolar
aka water and solute amount is proportional
LI does net absorb of ____ and secretes ____.
absorb - water, Na, Cl
secrete - K, bicarb
where does Cl drive fluid secretion? how?
crypts
by decreasing electronegativity, so cause Na drag
____ stim of the luminal surface triggers Cl secretion via ___ plexus
mechanical
submucosal plexus
describe mechanical stim of luminal surface causing Cl secretion
stroking stim -> PG release -> direct/indirect secretomotor neuron action -> VIP release -> Cl secrete
what’s the important GI regulator for Cl?
CFTR
CFTR information
membrane protein
anion channel
ATP dependent
describe how to activate CFTR
increased cAMP -> activate pKA -> phosphorylate channel -> Cl release
which agonists are able to activate both basolateral K channel and CFTR?
Ach, histamine, bile acids
how does cholera toxin relate to CFTR?
toxin activates intracell G protein -> activate adenylyl cyclae -> opens CFTR
what’s the importance of Na/glc and Na/aa cotransporter?
secondary active
fluid reuptake in GI
what is oral rehydration therapy?
makes use of SLUTGLUT in SI to help reabsorb glc and Na to rehydrate
what channel is essential for colonic reserve capacity?
ENac
what does ENaC do in colon?
selectively permeable for Na
aldosterone - activates Na/K pump, trigger insertion of preformed Na channel, trigger expression of new channel proteins
aldosterone alters the rate of _____ via ENaC
insertion, degreadation, recycling
what is amiloride?
aldosterone antagonsit that blocks ENaC
inhibits Na absorption in distal colon
promotes loss of Na and water
how is K affected by amiloride?
hyperkalemia
since ROMK also affected if ENaC is affacted
how is K absorbed in intestines?
how does major water loss affect K?
causes hypokalemia
how is Cl absorbed in intestines?
voltage dependent Cl absorb - passive paracell and transcell driven by electrochemical gradient (SLUTGLUT or ENaC)
electrochemical Cl/bicarb exchange
where is the Cl/bicarb exchanger present?
ileum and proximal colon
net move of bicarb into gut to increase pH
why is Na/H triggered by high luminal pH?
since secretin stim via decreased pH of food bolus arriving in duodenum
what is coupled in ileum and proximal colon for NaCl absorb?
Cl/bicarb and Na/H
describe D after surgical resection of major part of ileum?
