Cardiac cycle & the mammalian heart (Edexcel Int. A-level Biology)

This fully-resourced lesson describes the key events that occur during the three stages of the cardiac cycle and relates these to the structure of the mammalian heart. The engaging and detailed PowerPoint and accompanying resources have been designed to cover point 1.8 of the Edexcel International A-level Biology specification

As the structure of the heart was covered at iGCSE, the lesson has been planned to build on this prior knowledge whilst adding the key details which will enable students to provide A-level standard answers. The primary focus is the identification of the different structures of the heart but it also challenges their ability to recognise the important relationship to function. For example, time is taken to ensure that students can explain why the atrial walls are thinner than the ventricular walls and why the right ventricle has a thinner wall than the left ventricle. Opportunities are taken throughout the lesson to link this topic to the others found in topic 1 including those which have already been covered like the blood vessels. There is also an application question where students have to explain why a hole in the ventricular septum would need to be repaired if it doesn’t naturally close over time.
The next part of the lesson introduces the cardiac cycle through the use of quick quiz competition which generates the key term systole. Students will learn that there are three stages in the cycle are atrial and ventricular systole followed by cardiac diastole and that the uni-directional movement of blood during these stages is maintained by the atrioventricular and semi-lunar valves. This leads into the emphasis of the key point that pressure changes in the chambers and the major arteries is the cause of the opening and closing of these sets of valves. Students are given a description of the pressure change that results in the opening of the AV valves and shown where this would be found on the graph detailing the pressure changes of the cardiac cycle. They then have to use this as a guide to write descriptions for the closing of the AV valve and the opening and closing of the semi-lunar valves and to locate these on the graph. By providing the students with this graph, the rest of the lesson can focus on explaining how these changes come about. Students have to use their current and prior knowledge of the chambers and blood vessels to write 4 descriptions that cover the cardiac cycle. The final part of the lesson covers the changes in the volume of the ventricle.

It is estimated that it will take in excess of 2 hours of allocated A-level teaching time to cover the detail included in this lesson as required by this specification point