Cardiac Action Potentials (Mine) Flashcards
In what order does the action potential in the heart spread?
SA node
AV node
Bundle of His
R/L Bundle Branch (left is more subdivided)
Purkinje Fibers
Which areas can have pacemaker properties under the right conditions?
What keeps all these areas from trying to be pacemakers all at the same time?
SA node (generates AP most frequently)
AV node (delay at AV node)
Purkinje fibers (least frequent)
Overdrive Suppresion maintains order of pacemakers
What is the conduction velocity of the following?
- Atria:
- AV node:
- His-Purkinje:
- Ventricle:
- 1m/s
- 0.01-0.05m/s
- 2-4m/s
- 1m/s
What is the rule of thumb when it comes to velocity in terms of diameter?
What is the order of velocity from most to least
cells/fibers with larger diameters are faster
purkinje>atrial/ventricular muscle>AV node
Which atrium fires first, left or right?
Which layer fires first, endocardium or epicardium?
Which ventricle epicardium fires first, right ventricle or left ventricle?
Right atrium fires first
Endocardium fires first
Right ventricle epicardium fires first
know how to draw and label the cardiac action potential diagrams with labels for the ventricle, atrium, and SA node on slide 8
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Phase 0
what’s open and what’s closed?
Voltage gated Na channels open
IK1 close
depolarization stage
Phase 1
What’s open and what’s closed?
Inactivation gates of Voltage Gated Na channels close
Ito opens
this causes the dip between 1-2
Phase 2
What’s open and what’s closed?
Ca opens
Ito closes (which kicks of phase 2)
Iks open
plateau
Phase 3
What is open and what is closed?
Ca closed
Ikr and Iks reach max openess
rapid repol due to Ik1 opening
repolarization
Which K channel opens at phase 3’s peak?
IKr, IKs (rapid/slow)
Phase 4
What’s open/closed?
leaky K channels and other maintanance channels to keep membrane at rmp.
How does Na enter the cardiac myocytes?
Via voltage-gated Na channels
this is important for refractory periods
Inward Ca movement from L type Ca channels are somewhat responsible for which phase?
Phase 2
Transient outward K movement (Ito) are partially responsible for which phase?
Phase 1