1. Plasma is a constituent of blood.   True   False   2. During the atrial systole, the openings of the pulmonary vein and the vena cava are _______.   open   closed   3. During the ventricular systole, the blood enters the ventricles.   True   False   4. During the atrial systole, the atrial muscles _______.   relax   contract   5. Which fluid fills up the space between all human body cells?   intracellular fluid   extracellular fluid   intercellular fluid   extercellular fluid   Hint Half-n-half Clue   6. The cardiac veins carry blood to the walls of the heart.   True   False   7. The left auricle of the heart receives _______ blood from the lungs.   deoxygenated   oxygenated