Muscle, Locomotion and Heart

Abstract

Definition of muscle positive work, isometric contraction and negative work. Location of containing and force transmitting structures. Neuromuscular transmission. Twitch, clonus and tetanus. Mechanical structures in series and in parallel. Muscle and sarcomere force-length and force-velocity relations with their mechanisms and functional consequences. Subdivisions and meaning of the heat produced by muscle. Locomotion: internal and external work. Walking. Running, hopping and trotting. Enhancement of muscular work induced by previous muscle stretching. The heart. Action potential. Pressure-volume changes in the cardiac cavities, in the aorta and in the pulmonary artery as a function of time during a heart cycle. The Starling law providing that the blood output of the left ventricle equals the blood output of the right ventricle. Pressure-volume diagram and work done by the heart ventricles. Cardiac output: stroke volume as a function of heart frequency. Efficiency of the heart: effect of stroke volume and heart frequency. Measurement of cardiac output: Fick’s principle and dye method.