Fig. 1.1 summarises blood flow through the right side of the heart over one cardiac cycle. Three boxes in Fig. 1.1 have not been completed. Fill in boxes 3, 5 and 7 in Fig. 1.1 using only the terms systole and diastole.
Impulses released by the SAN pass to the AVN, where a short delay occurs. Referring to Fig. 1.1, explain why it is important for the control of the cardiac cycle that there is a short delay at the AVN after impulses have been sent out by the SAN.
Blood pressure in the heart changes during the cardiac cycle. These changes bring about the opening and closing of the bicuspid and tricuspid (atrioventricular) valves and the aortic and pulmonary (semilunar) valves. Explain how changes in blood pressure make the tricuspid valve open, make the pulmonary valve open, and assist the flow of blood through the heart.