Heart Physiology - autorhythmic cells here, but slower...

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Heart Physiology - Electrical Events distribute impulses throughout the heart - Autorhythmic cells : cardiac cells with an unstable resting potential Kevin Kelleher, MTC Biology 211 Study Notes Exam 2 4 o spontaneously depolarize due to pacemaker potentials caused by gradual influx of sodium ions o into cell causing action potential o the impulse is transferred from atria to ventricles in a defined sequence through gap junctions between cells - sequence of excitation : o sinoatrial (SA) node : autorhythmic cells here are the fastest to generate impulses (~75/min, called sinus rhythm); hence, this is the heart’s pacemaker o atrioventricular (AV) node : receives impulses from SA node; fewer connections between cells delay impulse long enough for atria to complete contraction; also
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Unformatted text preview: autorhythmic cells here, but slower impulses (~50-60/min, called junctional rhythm), so these cells do not set the pace unless there is damage to SA node cells o atrioventricular (AV) bundle (bundle of His) : electrical connection between atria & ventricles; transmits impulse to ventricles o right & left bundle branches : sends impulse along cells of interventricular septum toward apex o Purkinje fibers : extend from inferior aspect of interventricular septum to apex & into outer walls of ventricles- irregular heart rhythms (arrhythmias): o fibrillation : rapid & irregular contractions defibrillation : electrical shock to heart to reset rhythm o ectopic focus: abnormal pacemaker; may be caused by drugs (caffeine, nicotine) or SA node damage o heart block: damage to AV node interferes with impulse transmission to ventricles artificial pacemakers can be used to deliver impulses Page3...
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Heart Physiology - autorhythmic cells here, but slower...

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