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23 Cards in this Set

  • Front
  • Back
Heart cells dominated slow Ca channels
SA & AV node
Heart cells dominated fast Na channels
Pukinje fibers, Atrium, Endocardium, Midmyocardium, Epicardium
Examples arrhythmia
Bradycardia (<60bpm), tachycardia (>100bpm) even with normal activation sequence, AV/conduction block, ecctopic sites w/ abnoraml sequence
Equilibrium potentials Na cardiac cell
+40mV thus it tends to cause depolarization from the -90mV resting
Equilibrium potentials Ca cardiac cell
+80mV thus it tends to cause depolarization from the -90mV resting
Role of voltage sensitive gated channels
The Na, Ca, K channels play small role in resting MP, since closed in that state
Na-K ATPase
pump K into cell & Na out of cell
Na-Ca exchanger
Utilizes Na gradient to pump Ca out of cell.
Fast response tissues
-description
-Where located
-This is an tissue that has voltage-sensitive kinetically rapid Na channels
-atria, conducting system (His bundle, fascicles, bundle branches, purkinje fibers), ventricles, atrioventricular bypass tracts
Shape of action potential
depends on differences and density of ion channels present
phase 0 (ventricular cells)
rapid depolarization
-threshold is met
-voltage dependent Na channels open
-Rapid Na influx (favorable gradient)
-Cell becomes depolarized (+65mV)
-Depolarization results in closure voltage gated Na channel (cessation Na influx)
-Depolarization also results in opening Ca channels but influx MUCH SLOWER
phase 1
repolarization
-transient efflux K via I(to) channel
-rapid decay Na channel
phase 2
plateau
-Continued Ca influx
-Minimal Na influx
both maintain prolonged depolarization and offset K current
phase 3
xxxx
-decay Ca influx
-Increase K current efflux
Both lead to return to resting MP
phase 0 (SA/AV nodal cell)
-channel characteristics
- L type Ca channel allows Influx of Ca (rather than Na)
L type channel -
1-slower conduction velocity than voltage dependent Na channel
2-longer time to reactivate
Causes arrhythmia
enhanced automaticity
triggered activity
reentry
Causes enhanced automaticity
Increase slope phasee 4 = increased pacemaker rate
beta adrenergic stim
hypokalemia
mechanical stretch
Hypokalemia
low blood K levels result in increased pacemaker rate
Causes decreased automaticity
Decreased slope phase 4 = slower pacemaker rate caused by:
1-Ach
2-hyperpolarization
Reentry arrhythmia
1/3 type of arrhythmia
-responsible clinically most relevant arrhythmias
-Occurs when propogating impulsef ails to die out after normal activation of heart and persists to reexcite heart after refractory period
Ventricular Arrhythmias
Ventricular Tachycardia
-sustained
-nonsustained
Ventricular fibrillation
Ventricular Extrasystoles
Supraventricular Arrhythmias
-atrial origin
Atrial origin
-atrial fibrillation
-atrial flutter
-atrial tachycardia
-ectopic focus (enhanced automaticity)
-intraatrial/sinoatrial reentry
-atrial premature beat
Supraventricular Arrhythmias
-AV Junction origin
AV Junction Origin
-Atrioventriculaar nodal reentrant tachycardia
-Atrioventricular reentrant tachycardia
-AV junctional rhythms