9700/12 Biology Oct Nov 2016 Online Test | Cambridge AS and A Level MCQ

Which sequence of letters correctly identifies the order of events during the cardiac cycle?
T atrial walls contract
U impulse is delayed a fraction of a second
V wave of excitation enters the atrioventricular node
W wave of excitation passes down the Purkyne tissue
X wave of excitation spreads from the sinoatrial node
Y ventricles contract