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The Cardiac Cycle

The Cardiac Cycle. Refers to the events of 1 complete heart beat Both atria & ventricles contract then relax (0.8 sec if beating 75x/min) Key terms to know Diastole - relaxation Systole - contraction Lub-dub - the sound created by the closing of the heart valves (AV and semilunar).

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The Cardiac Cycle

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  1. The Cardiac Cycle • Refers to the events of 1 complete heart beat • Both atria & ventricles contract then relax (0.8 sec if beating 75x/min) • Key terms to know • Diastole- relaxation • Systole- contraction • Lub-dub- the sound created by the closing of the heart valves (AV and semilunar)

  2. Left atrium Right atrium Left ventricle Right ventricle Ventricularfilling Mid-to-late diastole(ventricular filling) Filling Heart Chambers: Cardiac Cycle Figure 11.7, step 1a

  3. Left atrium Right atrium Left ventricle Right ventricle Ventricularfilling Atrialcontraction Mid-to-late diastole(ventricular filling) Filling Heart Chambers: Cardiac Cycle Mid-to-late diastole— bloodflows from the atria into the ventricles (both chambers are relaxed, AV valves open) then the atria contract to squeeze remaining blood into the ventricles

  4. Left atrium Right atrium Left ventricle Right ventricle Ventricularfilling Atrialcontraction Isovolumetriccontraction phase Mid-to-late diastole(ventricular filling) Ventricular systole(atria in diastole) Filling Heart Chambers: Cardiac Cycle

  5. Left atrium Right atrium Left ventricle Right ventricle Ventricularfilling Atrialcontraction Isovolumetriccontraction phase Ventricularejection phase Mid-to-late diastole(ventricular filling) Ventricular systole(atria in diastole) Filling Heart Chambers: Cardiac Cycle Ventricular systole— blood pressure builds before ventricles contract, when ventricles begin to contract pressure gets high enough opening the semilunar valves allowing blood to be pushed out to the lungs and body

  6. Left atrium Right atrium Left ventricle Right ventricle Ventricularfilling Atrialcontraction Isovolumetriccontraction phase Ventricularejection phase Isovolumetricrelaxation Mid-to-late diastole(ventricular filling) Ventricular systole(atria in diastole) Early diastole Filling Heart Chambers: Cardiac Cycle Early diastole— atria finish refilling, when the pressure in the atria exceeds the pressure in the ventricles the AV valves will open allowing blood to fill the ventricles  the cycle begins again

  7. Murmur- condition in which one of the valves is not functioning properly (could be an AV or semilunar valves) and blood can flow backwards/inefficiently through the heart.

  8. Which phase of the cardiac cycle does this picture show? How can you be sure?

  9. Factors that Affect CO 1. Venous return (amount of blood that enters the heart) • Inc. venous return  inc. stretching 2. How much the ventricle is stretched prior to contraction • Inc. stretching inc. force of contraction 3. High blood pressure

  10. Factors that Change Heart Rate • Crisis stressors • Electrical system of the heart is more strongly stimulated to beat  inc heart rate • Congestive heart failure • Heart “worn out” • digitalis (drug) prescribed, strengthens contractions to inc. cardiac output • Epinephrine & thyroxine increase heart rate • Electrolyte levels (ions) • Low calcium depresses heart; high calcium causes sustained contraction  can cause cardiac arrest • Low potassium  irregular heartbeat

  11. Physical Factors that Affect Heart Rate • Age – HR decreases with age (healthy) • Gender – Females > males • Exercise – increases HR • Body temp – higher temp increases HR

  12. The Cardiac Cycle • Refers to the events of 1 complete heart beat • Both atria & ventricles contract then relax (0.8 sec if beating 75x/min) • Key terms to know • Diastole- relaxation • Systole- contraction • Lub-dub- the sound created by the closing of the heart valves (AV and semilunar)

  13. Left atrium Right atrium Left ventricle Right ventricle Ventricularfilling Mid-to-late diastole(ventricular filling) Filling Heart Chambers: Cardiac Cycle Figure 11.7, step 1a

  14. Left atrium Right atrium Left ventricle Right ventricle Ventricularfilling Atrialcontraction Mid-to-late diastole(ventricular filling) Filling Heart Chambers: Cardiac Cycle Mid-to-late diastole— bloodflows from the atria into the ventricles (both chambers are relaxed, AV valves open) then the atria contract to squeeze remaining blood into the ventricles

  15. Why?

  16. Left atrium Right atrium Left ventricle Right ventricle Ventricularfilling Atrialcontraction Isovolumetriccontraction phase Mid-to-late diastole(ventricular filling) Ventricular systole(atria in diastole) Filling Heart Chambers: Cardiac Cycle

  17. Left atrium Right atrium Left ventricle Right ventricle Ventricularfilling Atrialcontraction Isovolumetriccontraction phase Ventricularejection phase Mid-to-late diastole(ventricular filling) Ventricular systole(atria in diastole) Filling Heart Chambers: Cardiac Cycle Ventricular systole— blood pressure builds before ventricles contract, when ventricles begin to contract pressure gets high enough opening the semilunar valves allowing blood to be pushed out to the lungs and body

  18. https://www.youtube.com/watch?v=rguztY8aqpk Left atrium Right atrium Left ventricle Right ventricle Ventricularfilling Atrialcontraction Isovolumetriccontraction phase Ventricularejection phase Isovolumetricrelaxation Mid-to-late diastole(ventricular filling) Ventricular systole(atria in diastole) Early diastole Filling Heart Chambers: Cardiac Cycle Early diastole— atria finish refilling, when the pressure in the atria exceeds the pressure in the ventricles the AV valves will open allowing blood to fill the ventricles  the cycle begins again

  19. Think about it… • What do you suspect happens to the coronary blood vessels as the heart goes through the cardiac cycle? • What would happen to them during systole? • What would happen to them during diastole?

  20. Coronary Blood Vessels • Feed the cardiac muscle with oxygen rich blood • The coronary vessels branch off of the base of the aorta • Only fill with blood when the pressure inside of the aorta is low and the blood flows back towards the heart https://www.youtube.com/watch?v=tBQa8IBzP6I&feature=related

  21. What happens to a heart if it can’t get enough oxygen? HEART ATTACK

  22. Why? http://www.youtube.com/watch?v=DGxS44-rcps https://www.youtube.com/watch?v=eTKICIpShaA&feature=related

  23. Factors that Affect CO 1. Venous return (amount of blood that enters the heart) • Inc. venous return  inc. stretching 2. How much the ventricle is stretched prior to contraction • Inc. stretching inc. force of contraction 3. High blood pressure

  24. Factors that Change Heart Rate • Crisis stressors • Electrical system of the heart is more strongly stimulated to beat  inc heart rate • Congestive heart failure • Heart “worn out” • digitalis (drug) prescribed, strengthens contractions to inc. cardiac output • Epinephrine increase heart rate • Electrolyte levels (ions) • Low calcium depresses heart, high calcium can cause sustained contraction leading to cardiac arrest • Low potassium causes irregular heartbeat

  25. Physical Factors that Affect Heart Rate • Age – HR decreases with age (healthy) • Gender – Females > males • Exercise – increases HR • Body temp – higher temp increases HR

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