Interaction of acoustic and biological waves in muscular tissue

Abstract

In studying biological tissues from the viewpoint of diagnosis of their structure and function, the wave processes revealing the active properties of tissues (muscles, nerves, brain, etc.) are of special interest. Muscular tissue is penetrated not only by a branched network of blood vessels with smooth muscles, but also by a branched network of nerve fibers. In these tissues, the waves of acoustomechanic (deformation) and electric (action potential, ion concentrations) nature with propagation velocities of close values (1‐100 m/s) can travel and interact [1‐3]. In this case, the “relativistic” effects connected with the finiteness (limitation) of the propagation velocity of information-carrying excitation signals in nerve fibers and tissues are possible [4]. In addition to mechanochemical processes, electrical processes proceed in muscular tissue, which are connected with the tissue excitation. Typically, an electric wave initiates a mechanical contraction of a muscle. Some facts testify to the interaction between these wave processes (muscular twitching, cramp, overstress, etc.) [5]. Muscle contraction can be initiated by a mechanical action [2], change in temperature, and other factors (including acoustic irradiation) [6]. It is also known that the deformation of tissue can change its electrical properties and, consequently, the conditions of the propagation of the excitation potential [7, 8]. In a number of papers, a fragmentary attempt to describe mathematically the muscle contraction under the action of the excitation potential and their interrelation was made [2, 7, 8]. However, no complete mathematical description of the interaction between electric and acoustic waves in the course of their propagation in a muscle can yet be found in the literature.