Electrophysiological and Histological Studies on the Human Skeletal Muscle Part I Electrical Constants of the Membrane of Human Skeletal Muscle Fibers

The isolated human rectus abdominis muscle and the pectoralis major muscle were used, and these muscles were mounted in constant-temperature bath containing oxygenated Tyrode's solution, and resting potential, action potential and electrical constants of the muscle fiber membrane were measured. 1. These muscles are considered to be suitable for the examination of human skeletal muscle fibers in vitro. 2. Resting potentials of the rectus abdominis muscle and the pectoralis major muscle are 77.2±7.8mV and 73.9±9.7mV repectively, and action potentials of these muscles are 93.9±9.7mV and 87.2 8.0mV respectively. These figures are in the same range of any other reported data of the mammalian muscle fiber, but distributions are little wider. 3. Durations of action potentials are about 1.9 msec. in both muscles. 4. Electrical constants of these muscles are as follows: τm(msec) ρ(μ) Rm (cm) Cm (μF/cm2) λ(mm) M. pectoralis major 7.25±2.14 33±5 1080±325 9.1±4.1 1.39±0.47 M. rectus abdominis 8.60±2.22 27±5 1228±187 6.1±2.3 1.15±0.2