Wood S A, Morgan D L, Gregory J E, Proske U
Department of Physiology, Monash University, Clayton, Victoria, Australia.
Exp Brain Res. 1994;98(1):101-9. doi: 10.1007/BF00229114.
This is a study of the tendon jerk reflex elicited by a brief stretch applied to the triceps surae muscle group in the chloralose-anaesthetised cat. The size of the recorded reflex depended on stretch parameters (optimum at 300 microns amplitude at a rate of 100 mm/s) and on how the muscle had been conditioned. A reflex elicited after a conditioning contraction at the test length was often twice as large as after a contraction carried out at a length longer than the test length. This difference was attributed to the amount of slack introduced in the intrafusal fibres of muscle spindles by conditioning. The question was posed, did ongoing fusimotor activity exert any influence on the size of the tendon jerk? Depolarization indices (DPI) were calculated from responses of muscle spindles to stretch and correlated with the level of reflex tension. Values of DPI obtained from afferent responses with and without repetitive stimulation of identified fusimotor fibres suggested that with the stretch parameters used here the main influence of fusimotor activity was that it removed any pre-existing slack in muscle spindles and thereby increased reflex tension. In the absence of intrafusal slack, stimulation of static and dynamic fusimotor fibres had little additional influence on the size of the reflex. It is concluded that much of the variability typically seen with tendon jerks is due to muscle history effects. Since in muscles which have not been deliberately conditioned there is commonly some slack present in spindles, activity in fusimotor fibres is likely to reduce slack and therefore increase reflex size.
这是一项关于在水合氯醛麻醉的猫中，对腓肠肌群进行短暂拉伸所引发的腱反射的研究。记录的反射大小取决于拉伸参数（在速率为100毫米/秒时，振幅为300微米时最佳）以及肌肉的预处理方式。在测试长度下进行条件性收缩后引发的反射通常是在比测试长度更长的长度下进行收缩后引发反射的两倍大。这种差异归因于条件性收缩在肌梭的梭内纤维中引入的松弛量。由此提出一个问题，持续的肌梭运动神经元活动是否会对腱反射的大小产生任何影响？去极化指数（DPI）是根据肌梭对拉伸的反应计算得出的，并与反射张力水平相关。从对已识别的肌梭运动纤维进行重复刺激和未进行重复刺激时的传入反应中获得的DPI值表明，在此处使用的拉伸参数下，肌梭运动神经元活动的主要影响是消除了肌梭中预先存在的任何松弛，从而增加了反射张力。在没有梭内松弛的情况下，对静态和动态肌梭运动纤维的刺激对反射大小几乎没有额外影响。得出的结论是，腱反射中通常看到的大部分变异性是由于肌肉历史效应。由于在未经过刻意预处理的肌肉中，梭内通常存在一些松弛，肌梭运动纤维的活动可能会减少松弛，从而增加反射大小。
