This detailed lesson describes and explains the pressure and volume changes and associated valve movements that occur during the cardiac cycle to maintain the unidirectional flow of blood. The PowerPoint and accompanying resource have been designed to cover the 5th part of point 3.4.1 of the AQA A-level Biology specification.
The start of the lesson introduces the cardiac cycle as well as the key term systole, so that students can immediately recognise that the three stages of the cycle are atrial and ventricular systole followed by diastole. Students are challenged on their prior knowledge of the structure of the heart as they have to name and state the function of an atrioventricular and semi-lunar valve from an internal diagram. This leads into the key point that pressure changes in the chambers and the major arteries results in 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.
This lesson has been written to tie in with the other uploaded lessons on the circulatory system as detailed in topic 3.4.1 (Mass transport in animals)