The heartbeat process

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  • Created by: Rachh
  • Created on: 07-01-13 13:15
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  • Blood enters the heart through the vena cava (right) and pulmonary vein (left).
    • It passes into the atria
      • There is higher pressure in the atria than in the ventricles, so the atrioventricular valves are forced open.
        • The sino-atrial node (SAN) sends out waves of electrical activity to the atrial walls. This causes the atria to contract, pushing blood into the ventricles.
          • The waves of electrical activity don't reach the ventricles due to non-conducting collagen tissue.
            • Instead, these waves are transferred to the atrioventricular node (AVN)
              • There's a slight delay before the AVN reacts so that the atria have emptied
                • The AVN passes the waves of electrical activity on to the bundle of His (a group of muscle fibres).
                  • They conduct the waves of electrical activity to the Purkinje fibres (the finer muscle fibres in the ventricle walls)
                    • The pressure in the ventricles is higher than the pressure in the pulmonary artery (right) and aorta (left), forcing the semi-lunar valves open.
                      • The Purkinje fibres carry the waves of electrical activity into the muscular walls of the ventricles, causing them to contract simultaneously from the bottom up.
                        • This pushes the blood out of the heart and into the pulmonary artery (to the lungs) and the aorta (to the body).


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