Regulation of muscle stiffness during periodic length changes in the isolated abdomen of the hermit crab.
Regulation of muscle stiffness during periodic length changes in the isolated abdomen of the hermit crab.
复制标题
寄居蟹离体腹部周期性长度变化期间肌肉僵硬的调节。
DOI：
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发表时间：
1997
影响因子：
2.5
通讯作者：
W. Chapple
中科院分区：
文献类型：
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作者：
W. Chapple
采用正弦振动和随机纵向振动的方法，研究了寄居蟹腹侧浅肌（VSM）的反射激活，同时记录了肌肉的长度、力和3个兴奋运动神经元的发放时间。在没有振动的情况下，两个较大的运动神经元的interspike间隔直方图是双峰的;切割感觉神经包含大部分的mechanoreceptor输入删除了短间隔的峰值在直方图中，表明受体是重要的，在维持紧张性放电。肌肉的振动引起运动神经元频率的反射性增加，其在初始峰值后习惯化，但在刺激的持续时间内保持高于控制水平。运动神经元频率随刺激幅度的均方根（rms）而增加。刺激期间的平均刚度约为被动肌肉刚度的两倍。反射并没有改变肌肉的动力学。根据长度和力信号的快速傅立叶变换计算估计的传递函数。对于3 - 35 Hz的频率范围，相干性> 0.9。在此范围内，反射激活和被动肌肉的刚度幅度逐渐增加;相位在10和20度之间。反射刚度随着刺激幅度的增加而降低，但在较大的幅度下，这种降低不太明显;在这个范围内，刚度由反射调节。诱发反射爆发的正弦频率约为6 Hz，与先前使用斜坡拉伸的测量结果一致。在反射兴奋，有一个增加的幅度的短间隔峰的interspike间隔直方图，这是减少时，大多数传入通路被删除。正弦振动期间运动神经元放电的相位直方图在约110 ms处具有峰值，这也表明反射的重要组成部分是通过来自机械感受器的直接投射。这些结果是一致的假设，一个强大的前馈调节腹部僵硬在连续的干扰是通过机械感受器信号的绝对值变化的力量;习惯的反射，其高阈值的低频干扰和肌肉的激活动力学进一步修改反射动力学。
Reflex activation of the ventral superficial muscles (VSM) in the abdomen of the hermit crab, Pagurus pollicarus, was studied using sinusoidal and stochastic longitudinal vibration of the muscle while recording the length and force of the muscle and the spike times of three exciter motoneurons. In the absence of vibration, the interspike interval histograms of the two larger motoneurons were bimodal; cutting sensory nerves containing most of the mechanoreceptor input removed the short interval peak in the histogram, indicating that the receptors are important in maintaining tonic firing. Vibration of the muscle evoked a reflex increase in motoneuron frequency that habituated after an initial peak but remained above control levels for the duration of stimulation. Motoneuron frequency increased with root mean square (rms) stimulus amplitude. Average stiffness during stimulation was about two times the stiffness of passive muscle. The reflex did not alter muscle dynamics. Estimated transfer functions were calculated from the fast Fourier transform of length and force signals. Coherence was >0.9 for the frequency range of 3-35 Hz. Stiffness magnitude gradually increased over this range in both reflex activated and passive muscle; phase was between 10 and 20 degrees. Reflex stiffness decreased with increasing stimulus amplitudes, but at larger amplitudes, this decrease was much less pronounced; in this range stiffness was regulated by the reflex. The sinusoidal frequency at which reflex bursts were elicited was approximately 6 Hz, consistent with previous measurements using ramp stretch. During reflex excitation, there was an increase in amplitude of the short interval peak in the interspike interval histogram; this was reduced when the majority of afferent pathways was removed. A phase histogram of motoneuron firing during sinusoidal vibration had a peak at approximately 110 ms, also suggesting that an important component of the reflex is via direct projections from the mechanoreceptors. These results are consistent with the hypothesis that a robust feedforward regulation of abdominal stiffness during continuous disturbances is achieved by mechanoreceptors signalling the absolute value of changing forces; habituation of the reflex, its high-threshold for low frequency disturbances and the activation kinetics of the muscle further modify reflex dynamics.