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23 Cards in this Set
- Front
- Back
Heart cells dominated slow Ca channels
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SA & AV node
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Heart cells dominated fast Na channels
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Pukinje fibers, Atrium, Endocardium, Midmyocardium, Epicardium
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Examples arrhythmia
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Bradycardia (<60bpm), tachycardia (>100bpm) even with normal activation sequence, AV/conduction block, ecctopic sites w/ abnoraml sequence
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Equilibrium potentials Na cardiac cell
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+40mV thus it tends to cause depolarization from the -90mV resting
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Equilibrium potentials Ca cardiac cell
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+80mV thus it tends to cause depolarization from the -90mV resting
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Role of voltage sensitive gated channels
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The Na, Ca, K channels play small role in resting MP, since closed in that state
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Na-K ATPase
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pump K into cell & Na out of cell
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Na-Ca exchanger
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Utilizes Na gradient to pump Ca out of cell.
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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 |
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Shape of action potential
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depends on differences and density of ion channels present
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phase 0 (ventricular cells)
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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 |
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phase 1
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repolarization
-transient efflux K via I(to) channel -rapid decay Na channel |
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phase 2
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plateau
-Continued Ca influx -Minimal Na influx both maintain prolonged depolarization and offset K current |
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phase 3
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xxxx
-decay Ca influx -Increase K current efflux Both lead to return to resting MP |
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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 |
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Causes arrhythmia
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enhanced automaticity
triggered activity reentry |
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Causes enhanced automaticity
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Increase slope phasee 4 = increased pacemaker rate
beta adrenergic stim hypokalemia mechanical stretch |
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Hypokalemia
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low blood K levels result in increased pacemaker rate
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Causes decreased automaticity
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Decreased slope phase 4 = slower pacemaker rate caused by:
1-Ach 2-hyperpolarization |
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Reentry arrhythmia
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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 |
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Ventricular Arrhythmias
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Ventricular Tachycardia
-sustained -nonsustained Ventricular fibrillation Ventricular Extrasystoles |
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Supraventricular Arrhythmias
-atrial origin |
Atrial origin
-atrial fibrillation -atrial flutter -atrial tachycardia -ectopic focus (enhanced automaticity) -intraatrial/sinoatrial reentry -atrial premature beat |
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Supraventricular Arrhythmias
-AV Junction origin |
AV Junction Origin
-Atrioventriculaar nodal reentrant tachycardia -Atrioventricular reentrant tachycardia -AV junctional rhythms |