Refractory period studies in a human neuromuscular preparation.

Abstract

S U M M A R Y A subtraction technique has been employed to study refractoriness in the median nerve and thenar muscles in man. The absolutely refractory periods of the distal motor nerve branches and of the muscle fibres were found to be similar, the majority being within the 2.5-3.0 ms range; the values were distributed in a unimodal manner. The relatively refractory periods of the motor nerve terminals were about 5 ms. In some experiments it was possible to record non-propagated potentials at the endplate zones of the muscle fibres.The concept of an inexcitable period after the discharge of an impulse was first described by Lucas (1909) in relation to frog sartorius muscle fibres and by Gotch (1910) during an investigation of frog sciatic nerve. A more extensive analysis of this phenomenon was subsequently made with the cathode ray oscilloscope by Gasser and Erlanger (1925); these authors described an 'absolutely refractory period' (ARP) after excitation during which a nerve or muscle fibre could not disclharge an impulse to a second stimulus. Later it was shown that small, non-propagated, membrane depolarisations ('local responses') could take place during this time (Hodgkin, 1938). The absolutely refractory period was succeeded by a 'relatively refractory period' (RRP) in which the membrane displayed a rise in threshold but could be excited nevertheless, provided relatively strong stimulation was used. During the RRP there was also a slowing of impulse conduction which was most evident close to the stimulating electrode. This last phenomenon introduces a complication into any study of nerve or muscle excitability in which recordings are made at a distance from the stimulating electrodes. Because of the slowing of impulse conduction in the RRP the time separating the arrivals of two impulses at a distant point

Electrophysiological features of the mouse tail nerves and their changes in chemotherapy induced peripheral neuropathy (CIPN)

“…A further difference concerning the two responses was shown by double stimuli experiments, where the SENS2 component was unaffected by interstimulus intervals as short as 8.5 ms, which were effective in abating the muscle response to less than 25% of its original value. Such result is in agreement with the postsynaptic nature of the muscle potential, with a much longer recovery time than the axonal generated SENS2 (Kopec et al, 1978). In conclusion, proximal stimulation of the mouse tail evoked orthodromic muscle responses and antidromic sensory responses, almost identical to those seen in the rat (Leandri et al, 2007).…”

Effects of age, temperature, and disease on the refractoriness of human nerve and muscle.

“…On the basis of the endplate potentials, the shortest ARP of the nerve fibres was estimated to be 1.8 ms at 340C and 400C, 2.9 ms at 280C, and 5.5 ms at 200C (Fig. 2); these estimates depended on the calculation of T' as described by Kopec et al (1978). The ARPs of the muscle fibres could also be derived from measurements of T'; the relatively large increase brought about by cooling is shown in Fig.…”

“…The technique for measuring refractoriness was that described by Kopec et al (1978); the same use has been made of the terms S2, S:1, for stimulation and R2, R:, for recording procedures. Figure 1 shows the most complete set of results obtained in a series of 10 experiments.…”

“…1). Figure 6 shows the recovery of muscle excitability in terms of the time elapsing between the onsets of the conditioning and test responses (R, and R: respectively); this time corresponds to T' as determined by Kopec et al (1978). As discussed by these authors, this time can be used in the calculation of muscle fibre ARPs.…”

“…A new technique was described by Kopec et al (1978) for studying the absolutely refractory periods (ARP) and relatively refractory periods (RRP) of nerve and muscle fibres in man. The technique involved stimulating median motor nerve fibres electrically and recording the responses evoked in the thenar muscles with surface electrodes.…”