Responses of human masseter motor units to stretch.
Responses of human masseter motor units to stretch.
复制标题
人类咬肌运动单位对伸展的反应。
DOI：
10.1113/jphysiol.1995.sp020582
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发表时间：
1995
期刊：
影响因子：
--
通讯作者：
M. Nordstrom
中科院分区：
文献类型：
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作者：
T. Miles;A. Poliakov;M. Nordstrom
1. 研究了咬肌单运动单元对拉伸的反射反应和表面肌电图。2. 在咬肌表面肌电图中，等距收缩下颌肌的控制拉伸引起了短潜伏期（10 - 15毫秒）和长潜伏期（35 - 70毫秒）的兴奋性反射反应。3. 大多数（65%）紧张性活跃的咬肌运动单元在反射的短潜伏期和长潜伏期都兴奋。刺激的时间决定了单元是在短潜伏期还是长潜伏期放电。如果一个非紧张性活跃的运动单元被刺激招募，它总是在长潜伏期释放。4. 虽然短潜伏期反应强烈的时间锁定在刺激上，但在反射的这一阶段，峰间间隔（ISIs）的缩短很少。在长潜伏期，ISIs的缩短更为明显和持久，这解释了为什么这一阶段产生了拉伸后的大部分反射力变化。5. 在成对同时活动的运动单元中，对相同拉伸的短潜伏期反应的大小有十倍的范围。6. 在测试的22个咬肌运动单元中，有相当一部分（35%）没有统计学上显著的短潜伏期反射反应。7. 与其他人类肌肉不同的是，Ia传入神经群和一些咬肌运动神经元之间没有功能联系。对于这一结果有两种可能的解释。短潜伏期，可能是单突触，传入输入可能不均匀地分布到人类咬肌运动神经元。或者，这些输入可能受到紧张性突触前抑制，这种抑制在整个咬肌运动神经元池中不均匀分布。
1. The reflex responses to stretch were studied in single motor units and the surface electromyogram in human masseter. 2. Controlled stretches of the isometrically contracting jaw‐closing muscles evoked short‐latency (10‐15 ms) and long‐latency (35‐70 ms) excitatory reflex responses in the masseter surface electromyogram. 3. The majority (65%) of tonically active masseter motor units were excited in both short‐ and long‐latency phases of the reflex. The timing of the stimulus determined whether the unit discharged in the short‐ or long‐latency phase. If a non‐tonically active motor unit was recruited by the stimulus, it invariably discharged in the long‐latency phase. 4. Although short‐latency responses were strongly time‐locked to the stimulus, there was very little shortening of interspike intervals (ISIs) in this phase of the reflex. The shortening of ISIs was more prominent and prolonged during the long‐latency phase, which explains why this phase produces most of the reflex force changes following the stretch. 5. Within pairs of concurrently active motor units there was a tenfold range in the size of the short‐latency response to the same stretch. 6. A substantial proportion (35%) of the twenty‐two masseter motor units tested had no statistically significant short‐latency reflex response. 7. In contrast to other human muscles, there was no functional connection between a population of Ia afferents and some masseter motoneurons. There are two possible explanations for this result. The short‐latency, presumably monosynaptic, Ia afferent inputs may not be uniformly distributed to human masseter motoneurons. Alternatively, these inputs may be subject to tonic presynaptic inhibition that is not uniformly distributed throughout the masseter motoneuron pool.