Electrolytes & Water

Question 1

list sources of enterosystemic fluids

Answer 1

Question 2

list losses of enterosystemic fluids

Answer 2

Question 3

is the absorptive capacity of the colon high?

Answer 3

YES

Question 4

what provides reserve capacity for colon?

Answer 4

colonic fluid
ENaC

Question 5

how does epithelium control enterosystemic fluid balance?

Answer 5

secretion - crypts of SI and LI
absorption - villi in SI

Question 6

what is water transfer linked to?

Answer 6

chyme
Na
Cl
K
bicarb

Question 7

SI is a net absorber of ____ and a net secretor of ___.

Answer 7

absorb - water, Na, Cl, K
secrete - bicarb

Question 8

SI fluid absorption is ____.

Answer 8

isomolar
aka water and solute amount is proportional

Question 9

LI does net absorb of ____ and secretes ____.

Answer 9

absorb - water, Na, Cl
secrete - K, bicarb

Question 10

where does Cl drive fluid secretion? how?

Answer 10

crypts
by decreasing electronegativity, so cause Na drag

Question 11

____ stim of the luminal surface triggers Cl secretion via ___ plexus

Answer 11

mechanical
submucosal plexus

Question 12

describe mechanical stim of luminal surface causing Cl secretion

Answer 12

stroking stim -> PG release -> direct/indirect secretomotor neuron action -> VIP release -> Cl secrete

Question 13

what’s the important GI regulator for Cl?

Answer 13

CFTR

Question 14

CFTR information

Answer 14

membrane protein
anion channel
ATP dependent

Question 15

describe how to activate CFTR

Answer 15

increased cAMP -> activate pKA -> phosphorylate channel -> Cl release

Question 16

which agonists are able to activate both basolateral K channel and CFTR?

Answer 16

Ach, histamine, bile acids

Question 17

how does cholera toxin relate to CFTR?

Answer 17

toxin activates intracell G protein -> activate adenylyl cyclae -> opens CFTR

Question 18

what’s the importance of Na/glc and Na/aa cotransporter?

Answer 18

secondary active
fluid reuptake in GI

Question 19

what is oral rehydration therapy?

Answer 19

makes use of SLUTGLUT in SI to help reabsorb glc and Na to rehydrate

Question 20

what channel is essential for colonic reserve capacity?

Answer 20

ENac

Question 21

what does ENaC do in colon?

Answer 21

selectively permeable for Na
aldosterone - activates Na/K pump, trigger insertion of preformed Na channel, trigger expression of new channel proteins

Question 22

aldosterone alters the rate of _____ via ENaC

Answer 22

insertion, degreadation, recycling

Question 23

what is amiloride?

Answer 23

aldosterone antagonsit that blocks ENaC
inhibits Na absorption in distal colon
promotes loss of Na and water

Question 24

how is K affected by amiloride?

Answer 24

hyperkalemia
since ROMK also affected if ENaC is affacted

Question 25

how is K absorbed in intestines?

Answer 25

Question 26

how does major water loss affect K?

Answer 26

causes hypokalemia

Question 27

how is Cl absorbed in intestines?

Answer 27

voltage dependent Cl absorb - passive paracell and transcell driven by electrochemical gradient (SLUTGLUT or ENaC)
electrochemical Cl/bicarb exchange

Question 28

where is the Cl/bicarb exchanger present?

Answer 28

ileum and proximal colon
net move of bicarb into gut to increase pH

Question 29

why is Na/H triggered by high luminal pH?

Answer 29

since secretin stim via decreased pH of food bolus arriving in duodenum

Question 30

what is coupled in ileum and proximal colon for NaCl absorb?

Answer 30

Cl/bicarb and Na/H

Question 31

describe D after surgical resection of major part of ileum?

Answer 31