Corda M, Pantaleo T, Calamai F
Arch Fisiol. 1979 Jun 30;71(1-4):241-63.
The arrangement of muscle spindles in m. ext. long. dig. IV has been examined by microdissection. It is confirmed that spindle systems generally appear to consist of individual receptors. Stimulation effects of fast motor fibres (conduction velocities greater than 12 m/sec) on the spindles of the same muscle were studied. Receptors were isolated with their nerves and the appropriate spinal roots, the latter ones were used for stimulating efferent fibres and recording sensory discharges. Single shocks to the ventral root filaments caused afferent responses ranging from a single action potential to a train of impulses. During repetitive stimulation (train of stimuli at frequency of 10 to 150/sec) a marked increase in afferent activity was found. Afferent activity could be driven by the frequency of stimuli ("driving") and the stimulus/action potentials ratio varied from 1:1 to 1:3 or more. The rate of sensory discharge depended on the frequency of stimuli: the maximum effect, was attained at 30 to 50 stimuli/sec and, in the most responsive receptors, up to 80 stimuli/sec. Slight increases of the initial lengths of the receptors caused facilitation of sensory responses to motor stimulation. Moreover, impairing effects, which appear during sustained or high-frequency stimulation, possibly related to fatigue in intrafusal neuromuscular transmission, could be relieved by increasing the initial length. The repetitive stimulation of fast fusimotor fibres increased both dynamic and static responses and also raised the afferent activity after a period of stretching, when usually a depression occurs; these effects varied according to the preparation, its initial tension and the frequency of stimulation. The main feature of the examined motor fibres, when stimulated, is the constant excitatory action on muscle spindle static response. Results are discussed. It is suggested that the different characteristics of intrafusal muscle fibres, the receptor initial tension and the frequency of motor units discharges, may together affect muscle spindles static or dynamic performance.
通过显微解剖研究了第四趾长伸肌中肌梭的排列。已证实，梭系统通常似乎由单个感受器组成。研究了快肌纤维（传导速度大于12米/秒）对同一肌肉梭的刺激作用。将感受器与其神经及相应的脊神经根分离，后者用于刺激传出纤维并记录感觉放电。对腹根细丝的单次电击引起的传入反应范围从单个动作电位到一串冲动。在重复刺激（频率为10至150次/秒的刺激串）期间，发现传入活动显著增加。传入活动可由刺激频率驱动（“驱动”），刺激/动作电位比从1:1变化到1:3或更高。感觉放电率取决于刺激频率：最大效应在30至50次刺激/秒时达到，在反应最灵敏的感受器中，可达80次刺激/秒。感受器初始长度的轻微增加会促进对运动刺激的感觉反应。此外，在持续或高频刺激期间出现的损害效应，可能与梭内神经肌肉传递的疲劳有关，可通过增加初始长度来缓解。快肌梭运动纤维的重复刺激增加了动态和静态反应，并且在一段时间的拉伸后（通常会出现抑制）也提高了传入活动；这些效应因标本、其初始张力和刺激频率而异。所研究的运动纤维在受到刺激时的主要特征是对肌梭静态反应具有持续的兴奋作用。对结果进行了讨论。有人提出，梭内肌纤维的不同特性、感受器初始张力和运动单位放电频率可能共同影响肌梭的静态或动态性能。
