Are these valves are a kind of heart chambers pressure sensors?What is keeping them interlocked 2x2?
It's all mechanical. The valves are passive things kind of like a screen door. When you push on them from one side they open, when you push on them from the other they close. The valves are assisted by some fibers attached to the inside of the heart similar to the way a screen door is helped by a spring attached to the door frame. It's the flowing blood that pushes the valves open or closed as the heart pumps. The path that the blood follows in the heart as it beats happens to make it so that the valves close two at a time. This is because the heart is actually four separate pumps that work two at a time. There's no direct electrical connection to the SA node. The only way they're connected is that the SA node firing is what causes the heart to pump, causing the blood to force the valves open.
