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The heart cell with the strongest ___ drives the cardiac rhythm. Normally, this is the ___.
automaticity; sinoatrial node
___ is the sole pathway for electrical conduction between the atria and ventricles.
the AV (atrioventricular) node
Where is the AV node physically located?
in the right wall of the right atrium (near the opening of the coronary sinus and the tricuspid valve)
What four parts make up the His-Purkinje system?
1.) His Bundle (aka Bundle of His), 2.) Left Bundle Branch, 3.) Right Bundle Branch, 4.) Purkinje Fibers
What happens in the heart during diastole?
the atria and ventricles relax and fill with blood
Can an ECG show how well a heart is pumping?
no
What are myocytes?
the cells of the heart muscle
When at rest, the cells of the heart are ___, or negatively charged.  The myocardium contracts when the muscle cells ___.
polarized; become depolarized
On an ECG, the positive waveforms deflect ___ and the negative waveforms deflect ___.
upward, downward
While an ECG is being printed, the graph paper moves underneath the printhead at ___.
25 mm/second
The amplitude of a wave creates its ___, and this is measured in ___.
height or depth, voltage (mV; one square is equivalent to 0.1 mV)
One small box on an ECG graph paper is equivalent to ___ seconds.
.04 seconds
___ produces upright, or positive, defections on the ECG.
depolarization
A P wave always precedes a QRS complex and typically has a ___ morphology. In normal adults, the duration of the wave is between ___ with amplitude of ___.  If a wave fits this description, it most likely originated from the ___, making it a sinus P wave.
round, upright; .08 and 0.11 seconds; 0.5 to 2.5 mm; SA node
The PR interval encompasses all events from the firing of the ___ to ventricular ___ and typically lasts between ___.  Any PR intervals shorter than 0.11 seconds should be considered shortened. A PR interval longer than 0.20 seconds represents an ___.
SA node; depolarization; 0.12 seconds and 0.20 seconds; AV block
The shape of a wave on an ECG is referred to as its ___.
morphology
The 3 lead ECG system forms what is known as ___ triangle.
Einthoven's
Name the three augmented (aka ___) leads.
unipolar; aVR, aVL, aVF
What method is recommended to remember which leads are positive and negative in augmented leads?
Simply take the name of the lead and look at the last letter: aVR = Right arm is positive, aVL = Left arm is positive, aVF = Foot (left) is positive
V1-V6 leads are known as ___ leads.
precordial
If a premature complex appears every second beat, it is a ___. If every third beat, it is a ___. Every fourth beat is referred to as a ___.
bigeminy, trigeminy, quadrigeminy
While premature complexes occur early, ___ complexes occur later than expected.
escape
x of y cards