PHGY 213 Lecture Notes - Lecture 4: Qt Interval, Equipotential, Pr Interval
17 Mar 2017
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History ecg: first recordings of cardiac activity were not electrical, but rather mechanical, people used cardiograph / sphygmograph, place on wrist, pick up arterial pulse. In one of the leads there will be no q wave, in one lead there will be no s wave & some people will have upside down p or flat: everyone has different ecg. Normal activation sequence: sa node (right atrium), then right atrium / left after, two activations waveforms (one in left atrium and one slowly moving through. Internodal tracts: tracts that run in the atria, a bit like bundle branches (in green, don"t exist, but appear in textbooks. If have only q wave --quite wide --> depolarization of free walls. If double distance, voltage falls by 4 (to 1/4: this is why voltage at the body surface is so small --far from dipole source. If two points were on equipotential line, would pick up a voltage of 0 (same)
