Hoyle G
J Exp Biol. 1978 Apr;73:205-33. doi: 10.1242/jeb.73.1.205.
Muscle fibres of the locust extensor tibiae (jumping muscle) were examined by interference microscopy and by electron microscopy. The electrical responses of single fibres and the mechanical responses of bundles or selected regions to the nerve fibres were examined. Four axons innervate the muscle: fast (FETi), slow (SETi), common inhibitor (CI) and dorsal unpaired median (DUMETi). Their distributions were examined by combined electrophysiological tracing and EM sectioning. The mean diameter of muscle fibres in different regions varies from 40 to 140 micrometer and is related to the local leg thickness rather than muscle fibre type. The fine structure of a fibre is related to its innervation. Fibres innervated by FETi but not SETi are of fast type ultrastructurally. Fibres innervated by SETi but not by FETi are of slow type ultrastructurally. Fibres innervated by both axons are generally intermediate between the extremes though more nearly of fast type than slow. Distal slow muscle fibres have much slower relaxation rates than do proximal ones. The most proximal bundles are of mixed muscle fibre type. There is an abrupt transition from a mixed population to homogeneous fast type, in the muscle units immediately distal to the most proximal bundles. This transition is associated with the presence of DUMETi terminals on some of the fibres distal to the transition point. There are no SETi endings on these same fibres. Fibres innervated by both SETi and FETi are scattered throughout the leg, but are commonest in the dorsal bundles. The percentage of these increases progressively passing distally. The most distal muscle fibres are innervated by SETi but not by FETi. It is concluded that different regions of the muscle will play different roles functionally since they are differentially sensitive to the pattern of SETi discharge.
通过干涉显微镜和电子显微镜对蝗虫胫节伸肌（跳跃肌）的肌纤维进行了检查。研究了单根纤维的电反应以及肌束或选定区域对神经纤维的机械反应。有四条轴突支配该肌肉：快轴突（FETi）、慢轴突（SETi）、共同抑制轴突（CI）和背侧不成对正中轴突（DUMETi）。通过联合电生理追踪和电子显微镜切片检查了它们的分布。不同区域肌纤维的平均直径在40至140微米之间变化，并且与腿部局部厚度有关，而非与肌纤维类型有关。纤维的精细结构与其神经支配有关。由FETi而非SETi支配的纤维在超微结构上属于快肌纤维类型。由SETi而非FETi支配的纤维在超微结构上属于慢肌纤维类型。由这两条轴突共同支配的纤维通常处于两种极端类型之间，但更接近快肌纤维类型而非慢肌纤维类型。远端慢肌纤维的松弛速率比近端慢肌纤维慢得多。最近端的肌束是混合肌纤维类型。在紧邻最近端肌束远端的肌肉单元中，从混合类型突然转变为均匀的快肌纤维类型。这种转变与转变点远端一些纤维上存在DUMETi终末有关。在这些相同的纤维上没有SETi终末。由SETi和FETi共同支配的纤维散布于整个腿部，但在背侧肌束中最为常见。这些纤维的百分比向远端逐渐增加。最远端的肌纤维由SETi而非FETi支配。得出的结论是，肌肉的不同区域在功能上会发挥不同作用，因为它们对SETi放电模式的敏感性不同。
