Vicini EKG Flashcards
3 Requirements for effective heart pumping
- AV delay
- Synchronousity of V cells
- No tetanus
How long does cardiac cycle last?
1000 milliseconds
How long is systole relative to diastole?
Systole is about 2/3 the time
Phase 0 (3 facts)
- IKR is on at rest
- Na+ rapid upstroke
- Na+ inactivates at peak
Phase 1 (4 facts)
- Systole
- Regulated by IKR slowly shutting off
- Na+ closed
- Ca+ opens (plateau)
- K+ perm goes down
Phase 2 ( 3 Facts)
- Plateau phase via Ca trickle
- L-type Calcium Channel
- Ca & K counter balance maintains the plateau
Phase 3 (3 facts)
- Repolarization by K+ delayed rectifier
- (K+ efflux)
- Ca closes
Phase 4 (2 facts)
- KIR is on (Dia Rest)
- Ach is on too
Out of the 4 cardiac phases, which are sys and which are dia?
Phase 4 is Dia, everything else is Sys
Cardiac refractory period
Doesn’t allow another AP to avoid Tetanus. This is modulated during stress/exercise (longer/shorter refractory)
What’s a big regulator for pacemaker cells upstroke?
Calcium
What’s big for phase 4 in pacemakers?
Funny current
What is funny curent
Allows K, Na, and Ca all at once
3 factors that affect conduction velocity
- Ap upstroke velocity
- Cell size/ cytoplasm
- # of Gap junction
What happens in MI to heart ions?
- Na/K transporter gets messed up
- Extracellular K+ buildup b/c leaky ATP channels
- Na channels stop working because external voltage gets messed up
- Eventually Ca gets messed up
Pace maker Repolarization
K+ outflow
