Which one of the following statements is correct?
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.