HN220 Lecture Notes - Lecture 18: Cardiac Muscle, Chordae Tendineae, Atrioventricular Node
Document Summary
Atrioventricular (av) valves: right av valve = tricuspid valve, left av valve = bicuspid valve = mitral valve, papillary muscles and chordae tendinae, keep av valves from everting. Myocardial cells: 2 types of cardiac muscle cells (cardiocytes, contractile cells (myocardium, account for 99% of cardiocytes (cardiac myocytes, autorhythmic cells, can generate/spread ap spontaneously, pacemaker cells. Initiate aps and establish heart rate (rhythm; pace : conduction fibres, transmit/spread these generated aps, a key difference from skeletal muscle autorhythmicity (the ability to generate own rhythm) Contractile myocardial cells: are small (0. 2mm wide x 0. 1mm long, bifurcate, single centrally located nucleus, aerobic, high in myoglobin, high in mitochondria, extensive blood supply. The conducting system: pacemaker cells of the myocardium, sinoatrial node, pacemaker of the heart, atrioventricular node, conduction fibers of the myocardium. Internodal pathways: bundle of his, purkinje fibers, spread of excitation between cells, atria contract, then ventricles contract, coordination due to presence of gap junctions and conduction pathways.
