What occurs in the heart as blood moves from the atria into the ventricles?
- Aatria muscles: contract; atrioventricular valves: close; ventricle muscles: relax
- Batria muscles: contract; atrioventricular valves: open; ventricle muscles: relax
- Catria muscles: relax; atrioventricular valves: close; ventricle muscles: contract
- Datria muscles: relax; atrioventricular valves: open; ventricle muscles: contract