Power Output and Efficiency of Asynchronous Muscle

小行星9603187 能够进行高频操作的肌肉使用两种根本不同的模式之一来控制连接。 这两种模式的肌肉被称为同步或异步，这取决于肌肉电活动和肌肉收缩之间是否存在1：1的对应关系。 在同步肌肉中，短暂的收缩以及因此的高频率操作的可能性是通过肌纤维内的成分（T-小管和肌浆网）的精细加工来实现的，所述肌纤维通过钙释放和再结合参与收缩激活。 高频操作的异步方法建立在缩短失活和草图激活的基础上，这些特征在许多肌肉中发现，但在某些昆虫的高频肌肉中特别详细。 如果这些肌肉中的一个受到强直刺激，并以适当的频率进行周期性缩短和延长，则缩短期间任何给定长度处的力都大于再伸展期间该长度处的力，这是缩短失活的结果。 因此，在缩短过程中所做的功比重新拉长肌肉所需的功要多，并且存在净功输出，当肌肉附着在适当的共振负载上时，净功输出允许肌肉以高频重复收缩。 有人提出，异步肌肉应该有更高的质量比功率输出，比同步同行更有效率。 他们预计将有更大的功率输出，因为更少的空间需要专门用于控制组件（肌浆网和T-小管）在异步肌肉比同步的;更有效，因为钙循环的成本大大低于异步肌肉。 不幸的是，现有的信息的功率输出和效率的异步肌肉是不够的，知道假设是否正确。 这些假设将通过直接测量异步肌肉的功率输出和效率来进行测试。 所使用的肌肉是甲虫飞行肌肉，选择合适的大小和形状进行力学研究。 功率输出将使用工作回路方法确定，其中对肌肉施加重复的长度变化，并且每个循环的功率输出测量为当肌肉力相对于肌肉长度绘制时形成的图形的面积。 将在正常飞行期间的收缩频率和肌肉温度特征下进行测量。 功率测量将与能量消耗的测量相结合，通过氧气消耗或二氧化碳产生来判断，以确定肌肉将代谢能转化为机械能的效率。 ***

9603187 Josephson Muscles which are capable of high-frequency operation use one of two fundamentally different modes for controlling connection. Muscles of the two modes are termed synchronous or asynchronous, depending on whether there is or is not a 1:1 correspondence between muscle electrical activity and muscle contraction. In synchronous muscles brief contraction, and therefore the potential for high frequency operation, is achieved through the elaboration of the components within muscle fibers (the T-tubules and sarcoplasmic reticulum) which are involved in contractile activation through calcium release and rebinding. The asynchronous approach to high-frequency operation is built on shortening deactivation and sketch activation, features which are found in many muscles but which are particularly elaborated in high-frequency muscles of some insects. If one of these muscles is tetanically stimulated and subjected to cyclic shortening and lengthening at an appropriate frequency, the force at any given length during shortening is greater than the force at that length during reextension, a consequence of shortening deactivation. Thus more work is done during shortening than is required to relengthen the muscle, and there is net work output, work which allows the muscle to contract repetitively at high frequency when it is attached to an appropriate resonant load. It has been proposed that asynchronous muscles should have higher mass-specific power output and be more efficient than synchronous counterparts. They are expected to have greater power output because less space need be devoted to control components (sarcoplasmic reticulum and T-tubules) in asynchronous muscles than in synchronous ones; more efficient because calcium cycling costs are substantially less in the asynchronous muscles. Unfortunately, available information on power output and efficiency of asynchronous muscle is insufficient to know if the hypotheses are correct. These hypotheses will be tested by directly m easuring power output and efficiency of an asynchronous muscle. The muscle to be used are beetle flight muscles, chosen for being of convenient size and shape for mechanical studies. Power output will be determined using the work loop approach, in which a repetitive length change is imposed on the muscle and work output per cycle is measured as the area of the figure formed when muscle force is plotted against muscle length. Measurements will be made at a contraction frequency and muscle temperature characteristic of those during normal flight. Power measurements will be combined with measurements of energy expenditure, judged by oxygen consumption or carbon dioxide production, to determine the efficiency of the muscle in converting metabolic to mechanical energy. ***