bright_nnn
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the QRS interval
Because during this period the ventricular contraction occurs.But that shows the Ca+ conductance.
It could be the P wave.Please explain
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| Malaysian
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P waves has nothing to do with the ventricles....it shows atrial depolarization.QRS complex is the answer because the Na conductance causes the depolarization of the ventricles....the Ca+ channel opening as mentioned by you also occurs in the QRS complex....later when its only the K+ channel left to repolarize the ST segemnts are traced with the hyperpolarization measured by the T waves.
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| dxtxpx
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if someone can explain:
On page 77 of BRS physio 2nd ed
'QRS represents depolarization of ventricles'
then later it specifies saying
'ST segment represents the period when the ventricles are depolarized'
and then review test of this chapter 3 on page 111, there is a similar Q 17:
The ventricles are completely depolarized during which isoelectric portion of ECG? answer is ST segment
Can anyone explain, thanks :oops:
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| asmi
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yep QRS complex
Which segment of ECG represents completion ventricular repolarisation ?
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| rida
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I think what you are thinking is exactly how i was thinking before and was confused as well. The definition of ST segment is from the END of s wave to the BEGINNING of T wave, so that is the little interval during which the ventricle is still depolarized, if you look at the EKG in physio BRS pg 77, ventricular repolarization is the T wave, which begins rite AFTER ST segment. Hope i didn't confuse you further.
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| dxtxpx
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thanks rida, this was helpful
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| rida
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 glad i could help!
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| rida
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As per Asmi's questions, as far as which segment is concerned, i guess has to be QT, because its from depolarization to complete repolarization, but on the wave, T reperesents repolarization.
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| dxtxpx
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yes according to BRS: T wave rep ventricular repolarization
QT: entire period of depolarization and repolarization of ventricles
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| asmi
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answer to my Q is T wave.
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| rubensssss
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I guess answer will be QRS interval, because it said maximal vent Na channel conductance, when ventricular muscle initiade its depolaritation Na channel strat open and mantian its concentration, then in ST interval is depolarization complet but it concentration start to subside.
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| mani
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i think people here are confusing few things together:
QRS: beginning of depolarization
ST segment: duration in which ventricle is completely depolarized. no net current flow.
the original question was about max Na cnductance ie maz mumber of open sodium channels. this occurs during QRS.
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| rubensssss
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You are rigth mani.
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| bluestar
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while trying to relate ECG with action potential, can we say:
1, p wave on ECG :arrow: phase 0 on atrial action potential, which is Na+ inflow
2, QRS complex on ECG :arrow: phase 0 on atrial action potential, which is Na+ inflow
3, ST interval :arrow: completion of atrial membrane depolarization
4 T wave :arrow: phase 1,2 ,3 on ventrical action potential, which is accomplished by K outflow and Ca inflow.
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