This detailed and fully-resourced lesson describes and explains the pressure changes in the heart and arteries and the role of the valves movements in the cardiac cycle. The PowerPoint and accompanying resources have been designed to cover point 3.1.2 (f) of the OCR A-level Biology A specification and also covers the use of the equation stroke volume x heart rate to calculate cardiac output
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 next part 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. Moving forwards, the students are introduced to the stroke volume and meet normative values for this and for resting heart rate. This will lead into the calculation for cardiac output and a series of questions are used to test their ability to apply this equation as well as to calculate the percentage change which is a commonly assessed mathematical skill.
This lesson has been written to tie in with the other uploaded lessons on the topics detailed in module 3.1.2 (Transport in animals)