Which one of the following statements is correct?

During joint diastole stage AV valves open and passive filling of ventricle occurs. The tricuspid and the bicuspid valves open due to the fall in the ventricular pressure during the joint diastole itself (not during atrial systole). Increased ventricular pressure causes closing of the atrioventricular (bicuspid and tricuspid) valves. Atrial contraction is stimulated by the action potentials generated by the SA node.