Cardiac Conduction and APs Flashcards
ECG
Electrocardiogram
What does an ECG measure?
Extracellular voltage - difference between regions
P wave
Atrial depolarization (contraction)
At the peak of the P wave, what is contracting?
Right atrium
When the P wave returns to baseline, what is contracting?
BOTH atria
PR segment
Both atria contracting - baseline
QRS
Ventricular depolarization (contraction)
ST segment
Both ventricles contracting - baseline
T wave
Ventricular repolarization (relaxation)
The atrial T wave is hidden behind ____
QRS complex
R - R interval
Periods between ventricular depolarization
- determines heart rate
PR interval
Contraction and relaxation cycle of atria
QT interval
Contraction and relaxation cycle of ventricles
Bradycardia
HR < 60/min
Tachycardia
HR > 100/min
1st degree AV block
PR interval > 0.2 ms
What is the order that the action potentials spread?
SA node AV node Bundle of His R and L bundle branches Small purkinje fibers
Which atrium contracts first?
Right
Which layer of the heart contracts first?
Endocardium
Which ventricle contracts first?
Right
All portions of the action potential pathway can spontaneously generate action potentials under the right circumstances. What is the usual pacemaker of the cycle?
SA node
All portions of the action potential pathway can spontaneously generate action potentials under the right circumstances. What maintains the correct order?
Overdrive suppression
Cells with larger diameter have ______ signal propagation
FASTER
Compared to the AV node, purkinje fibers have ____ signal propagation
Faster
Which portions of the heart have cardiac FAST action potentials?
Atria, ventricles, purkinjes
Which portions of the heart have cardiac SLOW action potentials?
SA node and AV node