Heart Electrophysiology Flashcards
1
Q
Resting Membrane Potential is…
A
-90 mV
2
Q
Cardiac Glycosides
A
- increase contractility
- inhibit Na/K pump, which leads to accumulation of intracellular Na, which inhibits Ca/Na exchanger, leading to increased intracellular Ca concentration
- positive inotropic effect
3
Q
Digoxin
A
- a cardiac glycoside
- drug used to treat heart failure
4
Q
Autorhythmic cells
A
- small and do not contract
- conduct their own action potentials
- have Ifunny current, have pacemaker activity
- no resting membrane potential
5
Q
SA Node
Phase 0
A
- depolarization due to slow influx of Ca 2+ via L-Ca 2+ channels
6
Q
SA Node
Phase 4
A
- accounts for the drift
- major current is Ifunny
- spontaneous depolarization
- as drift gets close to threshold, T-Ca 2+ channels open, quickly bringing it to threshold, then close
7
Q
SA Node
Phase 3
A
repolarization due to efflux of K+
8
Q
Ventricles
Phase 0
A
fast influx of Na+
depolarization
9
Q
Ventricles
Phase 2
A
- plateau phase
- slow decay due to slow influx of Ca 2+ via L-Ca 2+ channels
- Ca induced release of Ca from SR
10
Q
Contraction
A
- AP down T tubule
- dihydropyradine channels open, Ca enters
- causes Ca release from SR
11
Q
Relaxation
A
- Ca from SR is pumped back into SR
- Na/K pump and Na/Ca exchanger bring potential back to normal
12
Q
Effect of Acetyl Choline
A
- when it binds to M2 receptors on SA node, it will decrease the rate of Phase 4 depolarization, and decrease the heart rate
13
Q
Effect of Atropine
A
- blocks M2 receptor, so increases heart rate
14
Q
Effect of Norepinephrine
A
- enhances opening of funny current
- increases heart rate
