Pathway of Conduction
Electrical Phases
EKG Manifestations
100
The pacemaker of the heart, so called because it is the fastest at electrical conduction.
Bonus: How many BPM can this generate?
The sinoatrial (SA) node.
50-200 BPM
100
Phase 0 and Phase 1 of electrical conduction through the heart correspond to this (name and what ions are involved).
Phase 0: depolarization (inward Na+ current)
Phase 1: initial repolarization (outward K+ current)
100
How much time is each small box worth on an EKG strip? Each big box?
0.04s/40ms
0.2s/200ms
200
The spontaneous generation of APs to create regular contractions is known as this. Which branch controls this feature of the heart?
What is automaticity? The ANS controls this.
200
Phases 2, 3, and 4 of electrical conduction through the heart correspond to this (name and what ions are involved).
Phase 2 - plateau (inward Ca++ current)
Phase 3 - rapid repolarization (outward K+ current)
Phase 4 - resting potential
200
What is the difference between a PR segment and a PR interval?
300
The order of electrical conduction through the heart.
300
What phases does the absolute refractory period span (1) and what does this mean (1)?
The absolute refractory period ranges from phase 0 to the beginning of phase 3 because Na/Ca channels are unable to open at this time.
300
This is a normal PR interval length.
120-200 milliseconds
400
What major change is seen on EKG the lower down the hierarchy a block occurs?
QRS widening
400
What phases does the relative refractory period span (1) and what does this mean (1)?
The relative refractory period ranges from the middle of phase 3 to the end of phase 4 because the cell can depolarize if above-normal Na+ concentrations are reached.
400
This is a normal QT interval length.
Around 400-440 milliseconds.