EKG Flashcards
What do open sodium channels cause?
a rising phase of the action potential (depolarization)
What happens when calcium is released?
couples the depolarization wave to the myofilaments
What happens when potassium channels open?
resting membrane potential is restored (repolarization)
How does the electrical impulses travel through the heart?
SA node to AV node to AV bundle (Bundle of His) to the right and left bundle branches and end at the purkinje fibers
What does the p wave represent?
atrial depolarization
What does Q represent on the EKG?
depolarization of the ventricular septum
What does R represent?
repolarization of the distal 1/3 of the ventricular septum
What does S represent?
depolarization of the remaining ventricle
What does T represent?
repolarization of the ventricle
What does the PR interval reflect?
conduction velocity through the AV nodde
What does the QRS complex represent?
ventricular depolarization
What does the QT interval represent?
the duration of depolarization AND repolarization of the ventricle
What happens with repolarization?
the heart relaxes
What happens with depolarization?
contraction
Which ventricle contracts first?
right
How long should the PR interval last? What is happening during this interval?
.12-.20 seconds. atrial depolarization
How long should the QRS complex last? What is happening during this time?
.08-.12 seconds. Ventricles are contracting
How long should the QT interval last? What is happening during this time?
less than .5 seconds. is the duration of depolarization AND repolarization of the ventricle
What is the time elapsed between each small box on an EKG?
.04 seconds
What is the time elapsed between each bolded box on an EKG?
.2 seconds
What does a premature atrial contraction look like on an EKG?
p wave immediately following the t wave