The Cardiac Cycle

Question 1

how is the heart beat coordinated

Answer 1

1. the sinoatrial node (SAN) , found in the right atrium, initiates a wave of depolarization that causes both the left and right atrium to contract
2. wave of excitation travels along the membrane tissue which cause the cardiac muscle to contract, an atrial systole
3. the wave is picked up by the atrioventricular node (AVN)
4. after a slight delay the AVN is stimulated and passes the stimulation along the bundle of His, which is made of purkinje fibers
5. at the apex the purkinje fibres cause ventricles to contract so blood is pushed up through the aorta and pulmonary artery