AQA as biology - cardiac Cycle

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  • Created by: maddie
  • Created on: 24-11-12 17:17
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  • Cardiac Cycle Summary
    • Continuos series of events making up a heart beat.
    • relaxation of the heart - Diastole
      • Blood returns to atria of heart via pulmonary vein and vena cava.
      • Atria fill up -> pressure in them rises -> atrioventricular (AV) valves open -> ventricle fill. Walls of atria and ventricles are relaxed.
        • relaxation reduces pressue in ventricle -> pressure lower than in aorta and pulmonary artery -> semi-lunar (SL) valves close, dub of heart beat
    • Contraction of atria (atrial systole)
      • atria walls contract -> remaining blood forced into ventricles. Ventricle walls are relaxed.
    • Contraction of vetricles (ventricular systole)
      • Ventricles fill with blood -> walls contract simultaneosly -> increased pressure within them _> Av valves forced shut preventing bacflow of blood , lub of heart beat.
        • Av valves closed, pressue rises , opening SL valves _> push blood into pulmonary artery and aorta.
      • Av valves closed, pressue rises , opening SL valves _> push blood into pulmonary artery and aorta.
      • walls of ventricle thick - pump blood to body. left ventricle thicker than right - L to body, R to lungs.
    • cardiac output
      • Volume of blood pumped by one verticle on one minute.
      • cardiac output = heart rate x stroke volume
        • stroke volume - vol of blood pumped in each beat
        • heart rate - rate at which heart beats

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