Gabriel, a heroin addict, feels tired, is weak and feverish, and has vague aches and pains. Terrified that he has AIDS, he goes to a doctor and is informed that he is suffering not from AIDS, but from a heart murmur accompanied by endocarditis. What is the most likely way that Gabriel contracted endocarditis? (Hint: See Related Clinical Terms.)

When the pressure inside the ventricle causes the atrioventricular valve to close and the semilunar valve to open, which statement about the heart is true?

For the atrioventricular valves to be open, the pressure in the ventricles must be:

What event immediately follows the closure of the atrioventricular valves and coincides with the onset of ventricular systole?

During which following phase (or phases) of the cardiac cycle is the blood volume in the ventricles constant?