Refractory Period in Human Sensory Nerve Fibres

Abstract

Relative and absolute refractory periods were determined in sensory fibres of 24 median nerves and in 19 sural nerves of 30 volunteers aged 20–60 years, who had no sign of a neuromuscular disorder. The critical interval of conduction (absolute refractory period) was found to be about 0.7 msec. In median as well as in sural nerve the relative refractory periods were about 5 times the absolute refractory period, measuring the amplitude, and about 3.5 times the absolute refractory period, measuring the latencies. Reasons for the reduction of amplitude and prolongation of latency during the relative refractory period are discussed. Slightly significant differences between the two age groups (20–35 and 40–60 years) have been found with respect to the relative amplitude in median nerves, but not in sural nerves and not with respect to the relative latency in either median or sural nerves.

Refractory period of human motor nerve fibres.

“…Gilliatt and Willison (1963), recording mixed nerve action potentials of the median nerve, reported absolute refractory periods of 0.6 to 0.7 ms. Buchthal and Rosenfalck (1966) measured a value of 0.75 ms in sensory fibres of the median nerve. Similar results were reported by Lowitzsch et al (1973), Hopf et al (1974), Tackmann and Lehmann (1974), and Betts et al (1976), all dealing with sensory or mixed fibres. An attempt to study ulnar motor fibres with paired stimuli was made by Wagman and Flick (1951) but the results were incomplete because the test response was not clearly isolated when using short interstimulus intervals.…”

“…It is known from studies of sensory and mixed fibres that nerve conduction is slowed during the relative refractory period (Gilliatt and Willison, 1963;Buchthal and Rosenfalck, 1966;Lowitzsch et al, 1973;Hopf et al, 1974;Tackmann and Lehmann, 1974;Hopf et al, 1976). Since, in our experiment, the latency was measured to the initial deflection of the compound action potential, latency changes evaluated were those of the fastest conducting fibres.…”

“…Although the refractory period has been examined in human sensory and mixed fibres (Gilliatt and Willison, 1963;Buchthal and Rosenfalck, 1966;Lowitzsch et al, 1973;Hopf et al, 1974;Tackmann and Lehmann, 1974;Hopf et al, 1976), studies of motor fibres have been limited previously to experimental animals. Gilliatt and Willison (1963), recording mixed nerve action potentials of the median nerve, reported absolute refractory periods of 0.6 to 0.7 ms. Buchthal and Rosenfalck (1966) measured a value of 0.75 ms in sensory fibres of the median nerve.…”

“…In 1963, Gilliatt and Willison reported the first comprehensive study on the refractory periods of human peripheral nerves. This and subsequent human studies, however, have been limited to sensory and mixed fibres (Buchthal and Rosenfalck, 1966;Lowitzsch et al, 1973;Hopf et al, 1974;Tackmann and Lehmann, 1974;Betts et al, 1976;Hopf et al, 1976). Muscle action potentials elicited by pairs of stimuli applied to motor fibres could not be measured accurately at short interstimulus intervals because of the overlap between conditioning and test responses (Wagman and Flick, 1951).…”

Refractory period studies in a human neuromuscular preparation.

“…Among the latter studies. the investigation of peripheral nerve by Gilliatt and Willison (1963) was noteworthy in that the significance of impulse slowing during the RRP was emphasised; more recent studies of nerve have been undertaken by Lowitzsch and Hopf (1972) and by Tackmann and Lehmann (1974). In all of the studies cited above the main trunks of peripheral nerves were examined and consequently there is no information presently available as to the refractoriness of the distal ramifications of sensory and motor nerve fibres.…”