1. During the atrial systole, the atrial muscles _______.   contract   relax   2. Plasma is a constituent of blood.   True   False   3. During the ventricular systole, the semilunar valves are closed.   True   False   4. During the ventricular systole, the blood enters the ventricles.   True   False   5. The process of circulation of blood in the heart begins with the _______ of the auricles of the heart.   contraction   relaxation   6. With reference to the heartbeat, the word 'systole' refers to a relaxation phase whereas the word 'diastole' refers to a contraction phase.   True   False   7. The left auricle of the heart receives _______ blood from the lungs.   deoxygenated   oxygenated