1. | Increased ventricular pressure causes closing of the semilunar valves. |
2. | The atrio-ventricular node (AVN) generates an action potential to stimulate atrial contraction. |
3. | The tricuspid and the bicuspid valves open due to the pressure exerted by the simultaneous contraction of the atria. |
4. | Blood moves freely from atrium to the ventricle during joint diastole. |
Doctors use a stethoscope to hear the sounds produced during each cardiac cycle. The second sound is heard when:
1. | AV valves open up |
2. | Ventricular walls vibrate due to the gushing of blood from the atria |
3. | Semi-lunar valves close down after the blood flows into vessels from the ventricles |
4. | AV node receives a signal from SA node |