Burrows M
Department of Zoology, University of Cambridge, UK.
J Comp Physiol A. 1995 Mar;176(3):289-305. doi: 10.1007/BF00219055.
Locusts (Schistocerca gregaria) use a distinctive motor pattern to extend the tibia of a hind leg rapidly in a kick. The necessary force is generated by an almost isometric contraction of the extensor tibiae muscle restrained by the co-contraction of the flexor tibiae (co-contraction phase) and aided by the mechanics of the femoro-tibial joint. The stored energy is delivered suddenly when the flexor muscle is inhibited. This paper analyses the activity of motor neurons to the major hind leg muscles during kicking, and relates it to tibial movements and the resultant forces. During the co-contraction phase flexor tibiae motor neurons are driven by apparently common sources of synaptic inputs to depolarized plateaus at which they spike. The two excitatory extensor motor neurons are also depolarized by similar patterns of synaptic inputs, but with the slow producing more spikes at higher frequencies than the fast. Trochanteral depressors spike at high frequency, the single levator tarsi at low frequency, and common inhibitors 2 and 3 spike sporadically. Trochanteral levators, depressor tarsi, and a retractor unguis motor neuron are hyperpolarized. Before the tibia extends all flexor motor neurons are hyperpolarized simultaneously, two common inhibitors, and the levator trochanter and depressor tarsi motor neurons are depolarized. Later, but still before the tibial movement starts, the extensor tibiae and levator tarsi motor neurons are hyperpolarized. After the movement has started, the extensor motor neurons are hyperpolarized further and the depressor trochanteris motor neurons are also hyperpolarized, indicating a contribution of both central and sensory feedback pathways. Variations in the duration of the co-contraction of almost twenty-fold, and in the number of spikes in the fast extensor tibiae motor neuron from 2-50 produce a spectrum of tibial extensions ranging from slow and weak, to rapid and powerful. Flexibility in the networks producing the motor pattern therefore results in a range of movements suited to the fluctuating requirements of the animal.
蝗虫（沙漠飞蝗）采用一种独特的运动模式，通过踢腿迅速伸展后腿的胫骨。所需的力量由胫节伸肌几乎等长收缩产生，该收缩受到胫节屈肌的共同收缩（共同收缩阶段）的限制，并借助股胫关节的力学作用。当屈肌受到抑制时，储存的能量会突然释放。本文分析了踢腿过程中主要后腿肌肉运动神经元的活动，并将其与胫骨运动和合力相关联。在共同收缩阶段，胫节屈肌运动神经元由明显共同的突触输入源驱动，达到去极化平台并在其上产生动作电位。两个兴奋性伸肌运动神经元也因类似的突触输入模式而发生去极化，但慢肌在较高频率下比快肌产生更多的动作电位。转节降肌高频发放动作电位，单根跗节提肌低频发放动作电位，共同抑制神经元2和3偶尔发放动作电位。转节提肌、跗节降肌和爪缩肌运动神经元发生超极化。在胫骨伸展之前，所有屈肌运动神经元同时发生超极化，两个共同抑制神经元以及转节提肌和跗节降肌运动神经元发生去极化。之后，但仍在胫骨运动开始之前，胫节伸肌和跗节提肌运动神经元发生超极化。运动开始后，伸肌运动神经元进一步超极化，转节降肌运动神经元也超极化，这表明中枢和感觉反馈通路都有贡献。共同收缩持续时间的近20倍变化以及快肌胫节伸肌运动神经元动作电位数量从2到50的变化，产生了一系列从缓慢微弱到快速有力的胫骨伸展。因此，产生运动模式的神经网络的灵活性导致了一系列适合动物不断变化需求的运动。
