Cardiac Electrophys (lec 1) Flashcards
Preload is?
stretch on vent at end diastole
Afterload is?
pressure against which heart pumps
2 types of heart cells?
myocardial
conducting
SNS effects on heart? (4)
↑ SA node pace ↑ A/V node impulse conduction ↑ contraction force coronary vasodilation constriction of peripheral bv = ↑ CO and BP
PNS effects on heart?
(vagus n)
↓ SA node pace
↓ AV node conduction
Properties of Myocardial cells? (4)
1) automaticity (produce impulse w/o outside stim
2) excitability (respond to stim)
3) conductivity (transmit impulse cell-to-cell)
4) contractility (contract when stimulated)
Properties of Pacemaker cells?
spontaneous generation of impulse (depol)
Properties of Conducting cells?
carry signal
Sinoatrial Node?
pacemaker
in posterior R atrium
60-100 bpm
Atrioventricular Node?
impulse pathway to vents
in low R atrium
40-60 bpm
Properties of Purkinje Fibers?
terminal branches of R/L bundles
20-40 bpm
take over for SA/AV nodes if fail
Polarized State is?
resting myo cells
- inside/+ outside
Depolarized State?
Na+ and Ca2+ enter cell
create AP
Repolarization?
Na+, Ca2+, K+ leave cell
Absolute Refractory Period?
temp resistant to depol
keeps depol wave moving forward
prevents spasm (continued contraction)
Relative Refractory Period?
in late repol, very strong signal can cause depol
Bipolar Leads?
+ and -
limb leads
Unipolar Leads?
+ only
chest/precordial
augmented limb
Upright Vectors?
show movement toward + electrode
Downward Vectors?
show movement away from +/towards - electrode
Biphasic Vectors (up and down)?
impulse perpendicular to + electrode
P Wave?
atrial depol
QRS Complex?
vent depol
T Wave?
vent repol
Atrial Repol where?
hidden in QRS
