This engaging lesson explores the roles of the SAN, AVN, Bundle of His and Purkyne fibres in the transmission of the wave of excitation through the heart. The PowerPoint and accompanying resources have been designed to cover the first part of point 6.1.3 of the AQA A-level Biology specification which states that students should be able to describe the myogenic stimulation of the heart and the subsequent wave of electrical activity.
The lesson begins with the introduction of the SAN as the natural pacemaker and then time is given to study each step of the conduction of the impulse as it spreads away from the myogenic tissue in a wave of excitation. The lesson has been written to make clear links to the cardiac cycle and the structure of the heart and students are challenged on their knowledge of this system from topic 3. Moving forwards, students are encouraged to consider why a delay would occur at the AVN and then they will learn that the impulse is conducted along the Bundle of His to the apex so that the contraction of the ventricles can happen from the bottom upwards. The structure of the cardiac muscle cells is discussed and the final task of the lesson challenges the students to describe the conducting tissue, with an emphasis on the use of key terminology