Editing Cardiac conduction system (section)

===SA node: P wave===
Under normal conditions, electrical activity is spontaneously generated by the [[SA node]], the cardiac pacemaker.  This electrical impulse is propagated throughout the right [[atrium (anatomy)|atrium]], and through [[Bachmann's bundle]] to the left [[atrium (anatomy)|atrium]], stimulating the [[myocardium]] of the atria to contract.  The conduction of the electrical impulses throughout the atria is seen on the [[ECG]] as the [[P wave (electrocardiography)|P wave]].<ref name=":0" /><ref>{{Cite web|url = http://sitemaker.umich.edu/ecgtutorial/cardiac_cycle|archive-url = https://archive.today/20150103040232/http://sitemaker.umich.edu/ecgtutorial/cardiac_cycle|url-status = dead|archive-date = January 3, 2015|title = Cardiac Cycle|access-date = January 2, 2015|website = ECG Tutorial|publisher = University of Michigan Health System}}</ref>

As the electrical activity is spreading throughout the atria, it travels via specialized pathways, known as ''internodal tracts'', from the SA node to the [[AV node]].