Lecture 13: Action Potentials and Conduction Flashcards
In what order do action potentials spread?
SA Node AV Node Bundle of His Right/Left Bundle Branch Purkinje Fibers
What is overdrive suppression?
SA node normally will prevent spontaneous generation of action potentials and allows synchronous contractions
What are the fastest cardiac cells/fiber?
- Purkinje Fibers
- Atrial and ventricle muscles
- AV node
Describe what is going on in phase 0 of cardiac action potentials for atria and ventricles.
Depolarization
-Voltage gated sodium channels are quickly opened and quickly shut (sodium enters cells)
Describe what is going on in phase 1 of cardiac action potentials for atria and ventricles.
Mini-Repolarization
-Voltage gated potassium channels are open (potassium leaves cells)
Describe what is going on in phase 2 of cardiac action potentials for atria and ventricles.
Plateau - Prolongs contractions
- Voltage gated calcium channels are open (calcium enters cell)
- Voltage gated potassium channels are open (potassium leaves cells)
Describe what is going on in phase 3 of cardiac action potentials for atria and ventricles.
Repolarization
- Voltage gated calcium channels close slowly
- Voltage gated potassium channels are open (potassium leaves cells)
Describe what is going on in phase 4 of cardiac action potentials for atria and ventricles.
Resting Potential
-Leaky potassium channels (potassium leaves)
Describe what is going on in phase 4 of cardiac action potentials for SA and AV nodes.
“Resting Potential”
- Funny sodium channels gradually depolarize (sodium slowly enters cell)
- even slower in AV node
Describe what is going on in phase 0 of cardiac action potentials for SA and AV nodes.
Depolarization
-Voltage gated calcium channels are open (calcium enters cell)
Describe what is going on in phase 3 of cardiac action potentials for SA and AV nodes.
Repolarization
-Voltage gated potassium channels are open (potassium leaves cells)
What is the supranormal period (SNP)?
Cell is more excitable than normal and it is easier to generate action potentials
-can have abnormal conduction
Why is not a good idea to have action potentials generated during RRP or SNP?
Conduction of action potentials will be weaker and that can cause issues with heart rate
What is chronotropy?
Changes in heart rate (slopes of phase 4 in SA/AV node modified)
What is dromotropy?
Changes in speed of conduction (slopes of phase 0 in SA/AV node modified)
