Cardiac Conduction Flashcards
cardiac conduction is initiated by what?
group of specialized cells called SA Node
SA Node have the ability to?
spontaneously depolarize (ie. autonomously generate AP)
electrical signal pathway
- SA node (through interconnected myocardial atrial cells)
- AV node
- Bundle of His
- bundle branches
- purkinje fibres
spontaneous depolarization of SA node is d/t to what?
plasma membrane of SA node cells being “leaky” to Na+
depolarization phase
slow influx of Na+ to threshold, then an influx of Ca2+
repolarization phase
flowing of K+ out of cell while Na+ and Ca2+ channels close
what happens at end of repolarization phase
K+ channels close and slow depolarization begins again
what does impulse derived from SA node do
initiate proper cardiac cycle and stroke volume
ECG
diagnostic tool that can detect abnormalities in cardiac conduction, ischemia, infarction, hypertrophy and electrolyte abnormalities
SA node is often referred as what?
cardiac “pacemaker”
how does ECG work?
placing electrodes on the skin and an electrical signal of the entire heart is observed
spontaneous depolarization of SA node prevents what?
prevents cells of SA node from ever achieving a true resting state (ie. as soon cells repolarize, depolarization starts again)
what does purkinje fibres do to electrical signal?
conduct signal to myocardium of ventricles, which contract simultaneously
how is the electrical signal when it reaches AV node?
signal is slightly delayed
