The diagram below shows a cross-section of the heart at the level of the valves.

a. i. Copy and complete the following flow chart to show the pathway of blood through the heart.

ii. Explain how the valves P and Q ensure one-way flow of blood through the heart.

b. The cardiac cycle describes the events that occur during one heart beat. The following figure shows the changes in blood pressure that occur within the left atrium, left ventricle and aorta during one heart beat.

Copy and complete the table below. Match up each event during the cardiac cycle with an appropriate number from 1 to 7 on the diagram. You should put only one number in each box. You may use each number once, more than once or not at all.

The first answer has been completed for you.

c. Explain the roles of the sinoatrial node (SAN), atrioventricular node (AVN) and the Purkyne tissue during one heart beat.

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