CPR 7.04 Cardiac Electrophysiology Flashcards
How would sympathetic activation of the heart affect the slope of phase 4 and the action potential threshold.
Increases slope
Reduces threshold
What effect would sympathetic activation of the heart have on I-f and L-type Ca++ channels?
- Increases I-f
- Opens Ca++ channels earlier
How would vagal activation of the heart affect the slope of phase 4 and the action potential threshold.
Decreases slope
Increases threshold
What effect would vagal activation of the heart have on I-f and L-type Ca++ channels?
Decreases I-f
Opens Ca++ channels later
What effect would vagal activation of the heart have on K-ACh channels and explain what this would accomplish
- Opens K-ACh channels.
- K interacts with K+ coupled Muscarinic channels
An increased K+ concentration will have what effect on HR?
Why?
Decreased HR
small increases in K+ opens K+ efflux channels and hyper polarizes the cell.
Hyperthyroidism will have what effect on HR?
Why?
Increased HR due to increased metabolism of nodal cells.
What effect will nodal ischemia/hypoxia have on HR and why?
Decreased HR due to decreased ATOP opening K ATP channels and causing hyper polarization
What is the pace set by AV node?
40-60bpm
What is the pace set by Purkinje fibers?
30-40bpm
Name something that pre-disposes a patent for after-depolarizations.
Prolonged QT syndrome: genetics, drugs, etc.
How are action potentials passed from cell to cell in the heart? (through what component of these cells?)
Low resistance gap junctions
Describe 1st degree AV block
Increased PR interval due to delayed condition through AV node, but still NSR
Describe 2.1 AV block
PR gradually lengthened, then drop QRS
Describe 2.2 AV block
PR fixed, but drop QRS randomly
Describe 3rd degree AV block
PR and QRS dissociated
Wht type of arrhythmia is Global reentry likely to cause?
Example?
SVT
WPW
Local reentry within atria or ventricles is likely to cause what types of arrythmias?
- Atrial tachycardia
- Vetnricular tachycardia
Local reentry within the AV node is likely to cause what type of arrhythmia?
SVT
What are the abnormal requirements in order for reentry to occur? (in regards to abnormal conduction in the heart)
- Partial depolarization of a conduction pathway
- Uniderectional block that only conducts AP in 1 direction
- Timing beyond the ERP
