Electrical Conduction in Heart

1) SA Node, 2) AV Node, 3) Bundle of HIS, 4) Purkinje fibers

Tachycardias = fast / Bradycardia = slow

Sites:
Heart Site: http://www.heartsite.com/html/electrical_activity.html
Wiki: http://en.wikipedia.org/wiki/Electrical_conduction_system_of_the_heart

Depolarization and the ECG

SA node: P wave (Atrial Systole, atrial repolarization)

AV node/Bundles: PR interval (Period of conduction)

Purkinje fibers/ventricular myocardium: QRS complex (Ventricular Systole, rapid ventricular depolarization)

Ventricular repolarization: T wave (Ventricular Diastole, ventricular repolarization)

ST Segment: The ventricles are repolarized

"also referred to as the isoelectric period, represents the period in which the entirety of both ventricles is depolarized. This roughly corresponds to the plateau phase of a ventricular action potential."

QT Segment: The time it takes for the DEpolarization AND REpolarization of the ventricles to occur

Videos:

EKG: http://www.youtube.com/watch?feature=player_detailpage&v=v3b-YhZmQu8