(a(i))[1]
State which label shows the valve that stops blood flowing back from the aorta into the ventricle.
(a(ii))[2]
Name the blood vessel that transports oxygenated blood from the lungs to the heart and state the label that represents this blood vessel. name ________ label ________
(b)[1]
State the exact location of the sinoatrial node.
(c)[2]
Explain the role of the atrioventricular node in coordinating heart action.