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Heart Actions

Heart Actions. Atrial Diastole /Ventricular Systole. Atrial Systole /Ventricular Diastole. 15-16. Cardiac Cycle. Atrial Systole/Ventricular Diastole blood flows passively into ventricles remaining 30% of blood pushed into ventricles A-V valves open/semilunar valves close

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Heart Actions

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  1. Heart Actions Atrial Diastole/Ventricular Systole Atrial Systole/Ventricular Diastole 15-16

  2. Cardiac Cycle • Atrial Systole/Ventricular Diastole • blood flows passively into ventricles • remaining 30% of blood pushed into ventricles • A-V valves open/semilunar valves close • ventricles relaxed • ventricular pressure increases • Ventricular Systole/Atrial diastole • A-V valves close • chordae tendinae prevent cusps of valves from bulging too far into atria • atria relaxed • blood flows into atria • ventricular pressure increases and opens semilunar valves • blood flows into pulmonary trunk and aorta 15-17

  3. Heart Sounds • Lubb • first heart sound • occurs during ventricular contraction • A-V valves closing • Dupp • second heart sound • occurs during ventricular relaxation • semilunar valves closing Murmur – abnormal heart sound 15-18

  4. Heart Sounds 15-19

  5. Cardiac Muscle • Short and branching cells • Connected by intercalated discs which contain gap junctions • Striated • Centrally located nucleus • Self stimulating and rhythmic • Can be influenced by nervous system • Use free fatty acids for energy • Life long cells • Replaced by scar tissue

  6. Cardiac Muscle Fibers • Cardiac muscle fibers form functional syncytia • group of cells that function as a unit • atrial syncytium • ventricular syncytium 15-20

  7. Cardiac Conduction System 15-21

  8. Cardiac Conduction System 15-22

  9. Muscle Fibers in Ventricular Walls 15-23

  10. Electrocardiogram • recording of electrical changes that occur in the myocardium • used to assess heart’s ability to conduct impulses P wave – atrial depolarizatoin QRS wave – ventricular depolarization T wave – ventricular repolarization 15-24

  11. Electrocardiogram 15-25

  12. Electrocardiogram A prolonged QRS complex may result from damage to the A-V bundle fibers 15-26

  13. Summary of Changes During Cardiac Cycle 15-27

  14. Regulation of Cardiac Cycle • physical exercise • body temperature • concentration of various ions • potassium • calcium • parasympathetic impulses decrease heart action • sympathetic impulses increase heart action • cardiac center regulates autonomic impulses to the heart 15-28

  15. Regulation of Cardiac Cycle Autonomic nerve impulses alter the activities of the S-A and A-V nodes 15-29

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