Anatomy unit 3 cardio and respiratory systems cardiac conduction notes

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Anatomy unit 3 cardio and respiratory systems cardiac conduction notes

  1. 1. UNIT 3 NOTES: Cardiac Conduction System
  2. 2. (1) Conduction System of Heart • Conduction System = Heart Beat & Pumping • Cardiac Contractions = Unconscious – Autonomic Nervous System  decrease or increase heart rate depending on circumstance
  3. 3. (2) Depolarization Path of the Heart • Describes the path the nerve impulses travel to make the heart contract and pump blood. • The Path: 1. 2. 3. 4. SA Node  AV Node Atria Contract (Delay)  AV Bundle Ventricles Contract (Blood ejected out of arteries, leaving heart)
  4. 4. (3) Nodes & Bundles • Sinoatrial Node (SA Node) – Right atrium – Starts each heart beat & sets rate – “Pacemaker” • Atrioventricular Node (AV Node) = Left atrium • AV Bundle = – Bundle Branches (along septum) – Purkinje Fibers (along entire muscular wall of heart)
  5. 5. (4) Cardiac Cycle Phase 1- Diastole (Relaxation) – Blood passively filling atria Phase 2-Systole (Contraction) – Ventricles contract – Blood Ejected out of heart
  6. 6. (5) Diastole Details 1. Ventricles relax 2. Semilunar valves closed 3. Ventricular Presure < Atrial Pressure – AV valves open – Ventricles fill with blood 4. Atria contract and force blood remaining in chambers into ventricles
  7. 7. (6) Systole Details 1. Pressure increases in ventricles - Filled with blood 2. AV valves close 3. Pressure in ventricles > Arteries leaving heart - Semilunar valves open Blood rushes out of ventricles 4. Atria are relaxed and begin to fill back up
  8. 8. (7) Heart Beat • You hear something like “lub” “dup” – “lub” = closing of AV valves • During ventricular systole – “dup” = closing of semilunar valves • During early diastole • You should NOT hear blood flow – You’ll hear it if flow is interrupted by blockage
  9. 9. (8) Starling’s Law • Starling’s Law of the Heart: – Degree of cardiac muscle extension before contraction – Increase Extension = Stronger Contraction – Degree of Extension  result of percent filling of ventricles

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