T wave on ecg

[Ravi Chaudhary]

Sorry if it appear ridiculous, but if the repolarization starts first from the cell which is last to depolarize and in opposite direction then why the T wave is not the exact mirror image of QRS complex??

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[Gurby]

I'll take a swing at answering:

When you depolarize, that's a wave of positive charge going outwards as cells go from -70mV up to +10mV or whatever.
As you repolarize, that's a wave of negative charge going inwards, as cells go from +10mV down to -70mV or whatever.

A positive wave going outwards gives us the same deflection as a negative wave going inwards. I think.

 

[Ravi Chaudhary]

I'll take a swing at answering:

When you depolarize, that's a wave of positive charge going outwards as cells go from -70mV up to +10mV or whatever.
As you repolarize, that's a wave of negative charge going inwards, as cells go from +10mV down to -70mV or whatever.

A positive wave going outwards gives us the same deflection as a negative wave going inwards. I think.

Thanks for your reply. But my question was not that why T wave is positive. In other words my question was- why T wave is round, dome-shaped why isn't it biphasic or involving 3 waves similar to QRS complex.

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[LChristmas]

Thanks for your reply. But my question was not that why T wave is positive. In other words my question was- why T wave is round, dome-shaped why isn't it biphasic or involving 3 waves similar to QRS complex.

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My guess is that repolarization is slower than depolarization, so the wave isn't as sharp.

 

[Instatewaiter]

Has to do with the ion channels which are used for each.