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Cardiovascular SystemChapter 11
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Conduction System• Intrinsic conduction system (nodal system)• Heart muscle cells contract, without nerve impulses!
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Conduction System• Sinoatrial node = SA node (“pacemaker”) • right atrium
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Conduction System• Atrioventricular node = AV node
• junction of the right atriumand right ventricle
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Conduction System• Atrioventricular bundle = AV bundle (bundle of
His) • In the interventricular septum
• Bundle branches
• Purkinje fibers (ventricle wall muscles)
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Heart Contractions• Contraction is initiated by the SA node• Impulse spreads to AV node, atria contract• Contraction is delayed• Passes through AV bundle, bundle branches and
Purkinje fibers• “wringing” contraction – begins at apex, moves
toward atria• Blood ejected
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Cardiac Cycle• Atria contract simultaneously• Atria relax, then ventricles contract• Systole = contraction• Diastole = relaxation
Atrialcontraction
Mid-to-late diastole(ventricular filling)
Ventricular systole(atria in diastole)
Early diastole
Isovolumetriccontraction phase
Ventricularejection phase
Isovolumetricrelaxation
Ventricularfilling
Left atriumRight atrium
Left ventricleRight ventricle
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• https://www.youtube.com/watch?v=T4x7-2HKtJ0
• https://www.youtube.com/watch?v=oHMmtqKgs50
• https://www.youtube.com/watch?v=qmpd82mpVO4
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• Cardiac output (CO)• Amount of blood pumped by each side (ventricle) of the
heart in one minute
• Stroke volume (SV)• Volume of blood pumped by each ventricle in one
contraction (each heartbeat)
• Heart rate (HR) • Typically 75 beats per minute