The firing rates of human motoneurones voluntarily activated in the absence of muscle afferent feedback.

摘要: 1. To quantify the net influence of muscle afferent feedback on firing rates human motoneurones, discharge frequencies single motor axons in common peroneal nerve were recorded during sustained voluntary efforts performed absence from target muscle. These data compared with units intact tibialis anterior In five subjects, recordings made fifty-two innervating acute deafferentation and paralysis dorsiflexor muscles produced by anaesthetic block distal to recording site. 2. Maximal sustainable determined for twenty-four motoneurons, twelve which classified as relatively low threshold (estimated recruitment level < or = 10% maximal) six high threshold. Mean low-threshold motoneurones (21.7 +/- 2.7 Hz; S.E.M.) significantly higher than those high-threshold (14.0 4.4 Hz). The mean rate deafferented maximal contract paralysed was 18.6 1.9 Hz, lower normally innervated (28.2 0.6 3. During half-maximal efforts, eight (10.8 1.1 Hz) that (16.5 0.2 A similar finding apparent minimal efforts; frequency seven weak 6.0 0.9 7.3 0.13 Hz units. Overall, range motoneurone (from levels effort) affected deafferentation, but shifted rates. 4. at least 30 s duration decreased over first 5 then maintained, i.e. there no progressive decline occurs fatiguing contractions. This observation supports a reflex origin normal discharge. 5. It is concluded afferents provide facilitation pool, reflexly increasing output all drive approximately one-third.