Electrical properties of spider leg muscle.

Abstract

Electrical properties of the spider muscle fiber were examined on M. flexor patellae longus and M. flexor patellae bilobatus of Atypus karschi DOENITZ. 1. The resting membrane potential ranged from -46 to -75 mV (mean -66 mV). 2. By stimulation of nerve strands, two kinds of responses, ‘fast’ and ‘slow’, were intracellularly recorded from a single muscle fiber. 3. ‘Fast’ responses consisted of initial slow and later abrupt rises of potential. The former is probably a junctional potential and the latter a spike having the all-or-none character. 4. ‘Slow’ responses are of graded and summative nature. 5. Most fibers produced only electrotonic and local potentials in response to direct catholdal polarization, but propagating action potentials were observed in a few cases. 6. The local potentials were oscillatory in most cases. The amplitudes of oscillations were, however, small compared to those in crustacean muscle fibers. 7. Electric constants of the fiber membrane were determined as follows: The effective resistance, Re, was 154.8 KΩ on the average; time constant, τm 7.9 msec.; specific membrane resistance, Rm, 131.7 Ωcm2; membrane capactiy, Cm, 60.6 F/cm2; and length constant, λ, 0.314mm in M. flexor patellae longus. The corresponding values obtained from M. flexor patellae bilobatus were as follows; Re 234.3 KΩ; τm, 14.3 msce.; Rm 504.4Ωcm2; Cm 28.9 μF/cm2; and λ 2.11mm. In these calculations the specific longitudinal resistance, Ri, was assumed to be 140 Ωcm. 8. The data were discussed from a comparative physiological point of view.