AQA as biology - cardiac Cycle
- 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.
- Ventricles fill with blood -> walls contract simultaneosly -> increased pressure within them _> Av valves forced shut preventing bacflow of blood , lub of heart beat.
- 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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