Session 13 Flashcards
(15 cards)
What is the role of the SA Node?
Pacemaker of the heart
The SA Node controls the heart rate and rhythm.
What is the resting potential of the SA Node?
-60mV
The SA Node does not have a true resting membrane potential.
What occurs during Phase 4 of the SA Node action potential?
Spontaneous depolarization
Continuous outward K+ leak and Na+ influx contribute to this phase.
What is the threshold for depolarization in the SA Node?
-40mV
At this threshold, T-type Ca++ channels open, leading to calcium influx.
What happens during Phase 0 of the SA Node action potential?
Depolarization occurs
L-type Ca++ channels open, depolarizing the cell to 0 mV.
What characterizes Phase 3 of the SA Node action potential?
Repolarization
K+ channels open to release K+, returning membrane potential to -60mV.
How does the action potential of the AV Node differ from the SA Node?
Slower Phase 0
This allows for proper ventricular filling.
What is the function of Purkinje Fibers?
Transmit impulses from apex to ventricles
They ensure synchronized contraction of the heart.
What is the inherent heart rate of the SA Node?
60-100 BPM
It serves as the dominant pacemaker.
What is the inherent heart rate of the AV Node?
40-60 BPM
It acts as a backup pacemaker.
What is the inherent heart rate of Purkinje Fibers?
20-40 BPM
These fibers serve as a backup pacemaker if SA and AV nodes fail.
True or False: Pacemaker cells have Phase 1 or 2 in their action potential.
False
Pacemaker cells do not have Phase 1 or 2 in their action potentials.
What facilitates depolarization in pacemaker cells?
Calcium
Calcium influx is crucial for the depolarization process.
How does the impulse transmission in the AV Node compare to the SA Node?
Slower
This slower transmission allows for proper ventricular filling.
Fill in the blank: The inherent rate of the dominant pacemaker is _______.
60-100 BPM
This rate is typical for the SA Node.
