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  #1  
Old 08-22-2015
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Default Hypokalemia

Does Hypokalemia increases or decrease potassium's conductance across the cell membrane?
I know guys this concept has been discussed all over the Internet with regards to Arrhythmias, but what I still don't understand is the above question.
I know that hypokalemia causes hyperpolarization. But hypokalemia means decreased concentration of K outside the cell. Inside, K is already too high, so now there should be an increased electrochemical gradient across the cell membrane and increased conductance of K too right?
Then why is it that with hypokalemia, K conductance decreases?
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Old 08-22-2015
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Quote:
Originally Posted by san.usmle View Post
Does Hypokalemia increases or decrease potassium's conductance across the cell membrane?
I know guys this concept has been discussed all over the Internet with regards to Arrhythmias, but what I still don't understand is the above question.
I know that hypokalemia causes hyperpolarization. But hypokalemia means decreased concentration of K outside the cell. Inside, K is already too high, so now there should be an increased electrochemical gradient across the cell membrane and increased conductance of K too right?
Then why is it that with hypokalemia, K conductance decreases?
The concentration of K will always be high in the cell as compared to outside whether theres hyper/hypo - kalemia. For "some reason" the conductance of potassium depends upon the extracellular concentration. So when theres hyperkalemia more channels are open and k goes out quickly during repolarization - short qt duration; while during hypokalemia less channels are open and k still goes out but because less channels are open that takes a long time - qt prolongs.
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Old 08-22-2015
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What you just explained totally makes sense and thanks for that. But still my qs is, why, or rather, how, more channels are opened during hyperkalemia as compared to hypo? Logically, shouldn't more channels be open during hypokalemia because of the greater K gradient across the cell membrane?
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Old 08-22-2015
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Quote:
Originally Posted by san.usmle View Post
What you just explained totally makes sense and thanks for that. But still my qs is, why, or rather, how, more channels are opened during hyperkalemia as compared to hypo? Logically, shouldn't more channels be open during hypokalemia because of the greater K gradient across the cell membrane?
Yes you are right but it doesnt happen that way..i wonder why too 😕

http://forums.studentdoctor.net/thre...gation.313878/

Check this
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Old 08-22-2015
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Ah, guess will have to just learn the conductance fact as it is then!
Thanks for all the input : )
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Originally Posted by san.usmle View Post
Ah, guess will have to just learn the conductance fact as it is then!
Thanks for all the input : )
I think i got it: hypokalemia would cause hyperpolarization because more force pushing k out and also the leaky channels pushing k out

Now what is conductance: it is basically "the rate of potential spread" . For a voltage sensitive channel the conduction velocity depends on the MP. The more - the membrane potential (mp) the faster the response. (Kaplan)

Therefore when hypokalemia causes hyperpolarization.. This makes it more negative and thus increases conductance.
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Old 08-23-2015
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But conduction decreases in hypokalemia!

All that you explained above: That's the thing, according to the logic & concept provided by kaplan, it should increase, but in reality, it rather decreases! The question remains, how?
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