Unit 1 - Cardiac Cycle
- Created by: sophieamyx
- Created on: 26-06-17 18:26
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- The Cardiac Cycle
- A sequence that contains contractions (systole) and relaxations (diastole) of the atria and ventricles
- Volumes of atria and ventricles change as they contract and relax
- Pressure changes also occurs due to changes in the chamber volumes
- Volumes of atria and ventricles change as they contract and relax
- Three stages of the Cardiac Cycle
- Stage 1: Ventricular diastole, atrial systole
- Ventricles relaxed
- Atria contracts, decreases volume of the chambers (blood is being squeeze out) and increases the pressure
- Pushes blood into ventricles
- Slight increase in ventricular press and chamber volume
- Pushes blood into ventricles
- Atria contracts, decreases volume of the chambers (blood is being squeeze out) and increases the pressure
- Ventricles relaxed
- Stage 2: Ventricular systole, atrial diastole
- Atria relaxed
- Ventricles contract, decreasing volume and increasing pressure in the chamber
- Pressure is now highest in the ventricles, so the valves snap shut
- Pressure in the ventricles is higher than the aorta and pulmonary artery, therefore the SL valve between opens, blood is forced out
- Pressure is now highest in the ventricles, so the valves snap shut
- Ventricles contract, decreasing volume and increasing pressure in the chamber
- Atria relaxed
- Stage 3: Cardiac diastole
- Both Ventricles and Atria relaxed
- Higher pressure in the pulmonary artery closes the SL valve, preventing backflow
- Blood flows back into the heart and starts to fill the atria again
- Atria pressure starts to increase
- Ventricles still relaxed
- Ventricular pressure falls below the pressure in the atria, opening the AV valves
- Blood flows passively from the atria into the ventricles
- Process restarts!
- Blood flows passively from the atria into the ventricles
- Ventricular pressure falls below the pressure in the atria, opening the AV valves
- Ventricles still relaxed
- Atria pressure starts to increase
- Blood flows back into the heart and starts to fill the atria again
- Higher pressure in the pulmonary artery closes the SL valve, preventing backflow
- Both Ventricles and Atria relaxed
- Stage 1: Ventricular diastole, atrial systole
- A sequence that contains contractions (systole) and relaxations (diastole) of the atria and ventricles
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