This 5-page worksheet product (with 2-page answer key) is designed to introduce upper middle school and high school anatomy students to the cardiac cycle, cardiac muscle, and ECGs. Topics include: blood flow through the heart, cardiac cycle steps, pressure changes during cardiac cycle, heart sounds, cardiac muscle, cardiac conduction system (SA node, AV node, etc.), electrocardiograms, intrinsic & extrinsic regulation of heart function, as well as the baroreceptor and chemoreceptor reflexes.