Cardiac Action Potentials Flashcards
What is the major cause of depol in neural AP
Na VGC
What channels maintain the RMP of a cell
K leak channels
What channels cause a repol of cell
Opening of K VGC
How does the AP from the Av node down travel
Through the IVS and back up to the atria
Which part of the heart receives action potential from depol first
What about for repol
Depol - endocardium first
Repol - epicardium first
Larger fibers have what in terms of transmission speed
Greater velocity
Which part of the electrical conduction system has the fastest conduction velocity
The purkinkie and atrial pathways
What does the delay at the AV Node allow for
Atria to completely empty into the ventricles before ventricular contraction
What is the RMP of ventricular and atrial myocytes compared to the SA Node and what does this mean
Vent/atria = -90
SA Node = -65
SA Node can depol much easier than myocytes
Define Na (M)
Activated when:
Action:
Phase:
Sodium VGC
Activated when: membrane potential crosses threshold
Action: opens very fast to allow for depol, then automatically closes (inactive gate) to allow for partial repol
Phase: 0 & 1
Define K(a)
Activated when:
Action:
Phase:
Potassium VGC
Activated when: cell depolarizes
Action:opens very rapidly, allowing for partial repol.
Phase: 1
Define Ca(L)
Activated when:
Action:
Phase:
Calcium VGC
Activated when: cell depol
Action: opens slowly and remains open to allow for prolonged plateau of phase 2. Closes allowing for phase 3 and repol.
Phase: 2 & 3
Define K(b) channel
Activated when:
Action:
Phase:
Activated when: cell depol.
Action: closes slowly and remains closed until it opens in phase 2, assisting with repol in phase 3
Phase: 2 & 3
Aka special rectifiers
Define K(c)
Activated when:
Action:
Phase:
Activated when: remains open
Action: maintains RMP
Phase: 4
Define Na(f)
Activated when:
Action:
Phase:
Activated when: SA or AP repol.
Action: opens to cause slow depol during resting phase (to get up to threshold for Na(m) to depol fully)
Phase: 4
The SA node depols faster or slower than other regions
Slower
What is the phase 4 build-up due to in the SA Node
Funny voltage-gated Na(f) channels
In the SA Node, what causes phase 0 and what is the significance of this
The opening of slow Ca channels and closing of special K(b) channels
This is the balancing act of Ca in and K out
What are the special K(b) channels in the SA node sensitive to
AcH (parasympathetic)
What causes phase 3 in the SA and AV nodes
The closing of Ca gates and opening of the K(b) gates
Phase 4 in cardiac myocyte sis sustained by what
K(c)
Define phase 1 of myocytes
A small repol caused by the closing of Na (m) and some K(a) opening
When do the inactivation gates of Na VGC close
Phase 1
What causes phase 2 in the myocytes
Slow opening of Ca VGC and closing of special K(b) channels
