The cardiac cycle


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The cardiac cycle

  1. 1. The Cardiac Cycle Charlotte Richardson
  2. 2. The cardiac cycleThis presentation goes through the stages of the cardiac cycle that occur in one heart beat.The cycle has been depicted here as starting from the end of diastole when the ventricles are relaxed and filled with blood.
  3. 3. Phase 1: Isovolumetric ContractionThe left ventricle isfull of blood andbegins to contract.This causes thepressure in the leftventricle to increase.
  4. 4. Phase 1: Isovolumetric ContractionOnce the pressure inthe left ventricleexceeds that of theleft atrium the mitralvalve will close.This is to preventblood from goingback into the leftatrium. Mitral valve closes
  5. 5. Phase 1: Isovolumetric ContractionThe ventriclescontinue tocontract, but until theaortic valve opens thepressure in the leftventricle increaseswith no change involume- this isisovolumetric Isovolumetriccontraction. contraction
  6. 6. Phase 2: Ventricular ejectionOnce the pressure inthe left ventricleexceeds that of theaorta the aortic valvewill open. Aortic valve opens
  7. 7. Phase 2: Ventricular ejectionBlood then leaves Ventricular ejectionthe left ventricle intothe systemiccirculation via theaorta- ventricularejection
  8. 8. Phase 3: Isovolumetric relaxationThe ventricles now Aortic valve closesbegin to relax oncethe blood has beenejected.When the pressurein the left ventriclefalls below that ofthe aorta the aorticvalve will close. Thisprevents bloodflowing back into theleft ventricle fromthe aorta.
  9. 9. Phase 3: Isovolumetric relaxationAs the ventriclesrelax the pressurewill fall, but therewill be no change involume until themitral valve opens-this is isovolumetric Isovolumetericrelaxation relaxation
  10. 10. Phase 4: Ventricular fillingOnce the pressure inthe left ventricle fallsbelow that in the leftatrium the mitralvalve will open.This then allows theventricles to fill withblood from the leftatrium, preparing Mitral valve opensthe ventricles foranother round of thecardiac cycle.
  11. 11. The cardiac cycle- recapPhases of the cardiac cycle: I. Isovolumetric contraction Systole II. Ventricular ejection III. Isovolumetric relaxation Diastole IV. Ventricular filling
  12. 12. The cardiac cycle- recap Ventricular ejection Aortic valve closes Aortic valve opens IsovolumetericIsovolumetric relaxationcontraction Mitral valve opens Mitral valve closes