A small cluster of cells located in the upper right atrium; it is the pacemaker of the heart.
SA Node
Inherent heart rate of the SA Node
60-100
Impulses sent by the SA Node travel through the atrial muscle fibers via the inta-atrial pathways; allows for simutaneous depolarization and contraction of the atria
Internodal pathways
Located in the lower portion of the right atria, receives impulses from the SA Node; delays the conduction to allow for the atria to contract, then conducts to the ventricles
AV Node
The AV Node has an inherent heart rate of
40-60
AV Node and the Bundle of His are collectively known as the
Junctional Area
AV Junction is the backup for the
SA Node
Arise from the bundle of His and travel down the right and left side of the septum
Right and Left Bundle Branches
Small branches of the bundle branches that spread throughout the ventricular myocardium and terminate there
Purkinje Fibers
The inherent heart rate of the ventricles is
20-40
_______ are the final back up pacemaker to the SA node and AV Junction/Junctional area
The Purkinje Fibers
The ability to act as an impulse, initiating electrical activity and spontaneous depolarization. Most important difference between cardiac and skeletal muscle cells
Automaticity
Most important difference between cardiac and skeletal muscle cells
Automaticity
The ability to respond to a stimulation and initiate an impulse
Excitability
The ability to transmit an impulse that has been initiated and passes along cell membranes
Conductivity
The inability of a muscle fiber to respond to a stimulus during an interval following contraction
Refractoriness
Time interval, when no matter how strong the stimulus, a cardiac cell cannot be depolarized. Measured from the beginning of the QRS complex to the middle of the T Wave
Absolute Refractory Period
Time interval, when given only a stronger than normal stimulus, a cardiac cell may depolarize. Known as the Vulnerable period because risk of R on T phenomnea. Measured from middle of T Wave to the end of T Wave
Relative Refractory Period
Conduction disturbances
Cardiac muscle mass
Incemia, Injury, or infarction
What ECG may provide information about
ECG does not provide information on ______
mechanical contraction (if the patient has a pulse)
The two most frequently used leads for cardiac monitoring are _______. ______ is perferred by most nurses because the waveforms are upright
lead 2 and v1. Lead 2
on ECG paper, one small box is ______ seconds long.
0.04
Represents atrial depoloarization
P Wave
Represents the time it takes for the impulse to pass from the SA node through atrial depolarization. Measured from the beginning of the P Wave to the beginning of the Q Wave. NORMAL LENGTH: 0.12 - 0.20 seconds
PR Interval
