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Natural Excitation of The Heart

Understanding the natural excitation and conductive system of the heart is crucial for managing heart conditions and rhythm disorders. This text delves into the SA node as the pacemaker, internodal pathways, AV node, Purkinje fibers, and the effects of the autonomic nervous system on cardiac rhythmicity. It also covers reentry phenomena and mechanisms, emphasizing the importance of maintaining a normal rhythm for cardiovascular health. Explore the spread of cardiac impulses, impulse velocity, Stokes-Adams Syndrome, and the reentry phenomenon in this comprehensive overview.

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Natural Excitation of The Heart

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  1. Natural Excitation of The Heart Guyton 2011 pages 115-120 Berne 2008 pages 302-309

  2. Natural Excitation of The Heart Excitatory and Conductive System of the Heart • To cause rhythmical contraction of the heart muscle • Conducting impulses rapidly through the heart. Is susceptible to damage by heart disease, especially by ischemia of the heart tissues

  3. Natural Excitation of The Heart SA Node = normal pacemaker • Pacemaker Cells (Small, round cells having few organelles and myofibril) Have two cell type • Conductor Cells (Slender, elongated cells) RMP is much less negative Lack the iKl, then the ratio of gK to gNa during phase 4 is much less

  4. Natural Excitation of The Heart SA Node = normal pacemaker Change the Heart Rate Change the slope of Phase 4 Change threshold Potential Change the RMP Normal rhythm = 70 – 80 beats/min

  5. Natural Excitation of The Heart SA Node = normal pacemaker Ca K Na , Ca Depolarization and repolarization is slower in slow responses

  6. Natural Excitation of The Heart Internodal Pathways

  7. Natural Excitation of The Heart AV Node Regions • AN region • (transitional zone) • N region • (mid portion) • NH region • Cause of the Slow Conduction • Mainly by diminished numbers of gap junctions Normal rhythm = 40 – 60 beats/min One-way conduction

  8. Natural Excitation of The Heart Purkinje fibers • Cause of the Rapid Conduction • mainly by increased numbers of gap junctions Normal rhythm = 15– 40beats/min

  9. Natural Excitation of The Heart Summary of the Spread of the Cardiac Impulse Through the Heart (second)

  10. Natural Excitation of The Heart Impulse Velocity in Different Part of the Heart

  11. Natural Excitation of The Heart Points Stokes - Adams Syndrome Ectopic Pacemaker Overrdrive Suppression

  12. Natural Excitation of The Heart Effect of ANS of cardiac rhythmicity

  13. Natural Excitation of The Heart Effect of ANS of cardiac rhythmicity • Parasympathetic division • Sympathetic division Mainly innervates nodes Innervates all areas • Acetylcholine • Norepinephrine • Increased permeability to K • Increased permeability to Na and Ca • Decreases Heart Rate • Increases the overall activity of the heart

  14. Natural Excitation of The Heart Reentry Phenomenon

  15. Natural Excitation of The Heart Reentry Mechanisms Pathway around the circle is too long Like cardiac dilation Velocity of conduction becomes decreased Blockage of the Purkinje system, Ischemia of the muscle, High blood potassium levels The refractory period of the muscle shortened in response to various drugs, such as epinephrine or after repetitive electrical stimulation

  16. Natural Excitation of The Heart Global Reentry

  17. The End

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