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Old 05-18-2013
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Default Increase in contractility


Got a question;
Reading FA; increase in Contractility (SA) with....:
3. Decrease in extracellular sodium (decrease activity of Na/Ca
exchange) :

here goes my question;
I get that the decrease in extracellular sodium causes the increase in contractility, but isn't it due to INCREASE Activity of Na/Ca pump? since if concentration of Na in the extracellular space low, Na tend to flow out from the inside exchanging with Ca ions flowing into the cell.

and another question goes:
How cause Acidosis decrease the contractility??

Thank you in advance!
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Old 05-18-2013
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hey,i shall attempt to answer - correct me if im wrong.

so i assume we are talking about digoxin/digitoxin acting on Na/K Atpase.
so when that (Na/KAtpase) is blocked - there is increased Na inside right.

so now the Na/Ca exchanger which normally works by getting Na inside and throwing Ca outside wont work - because there is Increased Na inside.
and so now there is also Increased Ca inside (because it is not thrown outside) --- increased contractility.

the acidosis leading to contractlity - im not sure how that works,what i do know is when metabolic acidosis (increased H) then K/H exchanger gets H to go in and K goes out so we get hyperkalemic Metabolic Acidosis.

please let me know if i have made a mistake,thanks.
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