What anatomical feature prevents the electrical signal from traveling directly from atrial muscle to ventricular muscle?

The first sound of a cardiac cycle occurs when the _____ and ______   (select them in alphabetical order) are closing.   The second sound of a cardicac cycle occurs when the  _______ and ________  (select them in alphabetical order)  are closing.   Word Options for Blanks: (some may not be used, some may be used more than once) aorta aortic valve bicuspid valve coronary sinus inferior vena cava left atrium left ventricle pulmonary arteries pulmonary trunk pulmonary valve pulmonary veins right atrium right ventricle superior vena cava tricuspid valve

What are the two functional importances of the intercalated discs of cardiac muscle?

mr. Holmes, a 72-year-old Caucasian male, suffered a heart attack which resulted in damage to a papillary muscle holding down the mitral valve. As a result the mitral valve is prolapsing with each heartbeat, which enables the backflow of blood. Where is this blood back flowing to? left ventricle, left atrium, or the aorta.