3 - SOME ASPECTS OF THE BIOPHYSICS OF MUSCLE

Abstract

This chapter presents some aspects of the biophysics of the muscles. Like nerve, muscle is excitable. It conducts electric current. It is capable of generating an electrical potential difference across barriers separating sarcoplasm from extracellular fluid. Under suitable circumstances, electrical properties of these barriers are altered and associated with these alterations. There are generated electrical currents and potential differences propagated along and through muscle fibers. There are two forms of spread of an electrical potential difference over the surface of a muscle fiber. The spread that occurs as though the fiber is passive is called “electrotonus.” In contrast, the propagated wave of altered electrical potential difference in response to a suitable stimulus resulting in the change in barrier properties is the action potential. The cable sheath or muscle membrane is made of a parallel unit that can carry current between the external solution and the core. The external solution and the cable core are considered purely resistive conductors. It is assumed that the total internal and the total external longitudinal currents flowing across any plane perpendicular to the axis of the cable are proportional to the longitudinal voltage gradient at the internal and external surface, respectively. The chapter also discusses the mechanical properties of single fibers and sarcomeres.