Department of Physics, Faculty of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo, Japan.
Prog Biophys Mol Biol. 2011 May;105(3):187-98. doi: 10.1016/j.pbiomolbio.2010.11.009. Epub 2010 Dec 14.
It is widely known that the contractile system of muscle takes on either the state of contraction (force-generating) or the state of relaxation (non-force-generating), which is known as the "all-or-nothing" principle. However, it is important to note that under intermediate activation conditions there exists a third state, which demonstrates auto-oscillatory properties and is termed SPOC (SPontaneous Oscillatory Contraction) state. We present a phase diagram, in which the states of the contractile system of muscle are divided into three regions consisting of contraction, relaxation and SPOC states. In the present review, experimental data related to the characteristics of SPOC are summarized and the mechanism of SPOC is described. We propose that the bio-motile system itself is an auto-oscillator, even in a membrane-less supra-molecular structure composed of an assembly of molecular motors and cytoskeletons (actin filaments and microtubules). Finally, the physiological significance of SPOC is discussed.
众所周知，肌肉的收缩系统呈现收缩（产生力）或松弛（不产生力）状态，这被称为“全有或全无”原则。然而，重要的是要注意，在中间激活条件下存在第三种状态，它表现出自发振荡特性，被称为 SPOC（自发振荡收缩）状态。我们提出了一个相图，其中肌肉的收缩系统的状态分为三个区域，包括收缩、松弛和 SPOC 状态。在本综述中，总结了与 SPOC 特征相关的实验数据，并描述了 SPOC 的机制。我们提出，生物运动系统本身就是一个自动振荡器，即使在由分子马达和细胞骨架（肌动蛋白丝和微管）组装而成的无膜超分子结构中也是如此。最后，讨论了 SPOC 的生理意义。
