Description: Segment 1 The basic anatomy of a heart is explained with the use of a dog's heart and labels. The beating of the heart is also shown in slow motion. A diagram shows a cross section of the heart. An animated diagram explains the movement of impulses across the heart. Time start: 00:00:00:00 Time end: 00:05:49:18 Length: 00:05:49:18 Segment 2 Intertitles explain various types of irregularities of the cardiac rhythm, including phasic sinus arrhythmia, sinus bradycardia and sinus tachycardia. Dogs' hearts are made to simulate these conditions. Time start: 00:05:49:18 Time end: 00:11:03:09 Length: 00:05:13:16 Segment 3 Intertitles explain various types of irregularities of the cardiac rhythm and how they can be caused, including idioventricular rhythms and premature systoles. Animated diagrams are used to show the travel of impulses across the heart in these types of irregularities, and dogs' hearts are used to show the different types of rhythmic irregularities. Time start: 00:11:03:09 Time end: 00:16:40:02 Length: 00:05:36:18 Segment 4 More types of irregularities are explained using animated diagrams, footage of beating dogs' hearts and intertitles. Irregularities addressed include paroxysmal tachycardia, auricular tachycardia, tachycardias of ventricular origin and auricular fibrillation. Time start: 00:16:40:02 Time end: 00:22:07:13 Length: 00:05:27:11 Segment 6 Complete heart block is explained, in which no impulses reach the ventricles. Footage of a beating dog's heart is shown. Time start: 00:27:01:10 Time end: 00:32:20:20 Length: 00:05:19:10