Richmond F J, Bakker G J, Bakker D A, Stacey M J
J Comp Neurol. 1986 Mar 22;245(4):483-97. doi: 10.1002/cne.902450405.
Patterns of innervation were examined in tandem muscle spindles teased from silver-stained muscles of the cat neck. Each tandem spindle was composed of two or more encapsulated receptors linked in series by a shared bag2 fiber. In most tandem spindles, two different types of encapsulation were identified according to differences in their intrafusal fiber content. One type, the b1b2c unit, contained typical bag1, bag2, and chain fibers and was structurally similar to single spindles described in other cat muscles. Each b1b2c unit contained a single primary sensory ending and 1-6 secondary endings. Fusimotor innervation was supplied by many axons. Some fusimotor axons ended in trail ramifications on bag2 and chain fibers, others ended in plates on the bag1 or long chain fiber. The other type of tandem encapsulation, the b2c unit, had only bag2 and chain fibers in its intrafusal fiber bundle. The b2c unit was usually supplied by only one sensory axon that ended on the nucleated part of the intrafusal fiber bundle. This single ending had a more variable terminal morphology than the primary ending in b1b2c units. A few b2c units (3/49) were also supplied by a secondary ending. The fusimotor innervation of the b2c unit was relatively simple. A single pole of the b2c unit was usually supplied by only one to three axons, all ending in trail ramifications. No plate endings were found in b2c units. These morphological specializations suggest that b1b2c and b2c units in tandem spindles differ in both their transductive and fusimotor mechanisms. Thus, the tandem spindle is a specialized structure that may provide additional proprioceptive information beyond that available from single muscle spindles.
对从猫颈部银染肌肉中分离出的串联肌梭的神经支配模式进行了研究。每个串联肌梭由两个或更多个被膜感受器组成，这些感受器通过一条共用的袋2纤维串联连接。在大多数串联肌梭中，根据其梭内纤维含量的差异，鉴定出两种不同类型的被膜。一种类型是b1b2c单元，包含典型的袋1、袋2和链纤维，在结构上与其他猫肌肉中描述的单个肌梭相似。每个b1b2c单元包含一个单一的初级感觉末梢和1 - 6个次级末梢。肌梭运动神经支配由许多轴突提供。一些肌梭运动轴突在袋2和链纤维上以追踪分支的形式终止，另一些则在袋1或长链纤维上以终板的形式终止。另一种串联被膜类型，即b2c单元，其梭内纤维束中只有袋2和链纤维。b2c单元通常仅由一个感觉轴突提供神经支配，该轴突在梭内纤维束的有核部分终止。这个单一的末梢的终末形态比b1b2c单元中的初级末梢更具变异性。少数b2c单元（3/49）也由一个次级末梢提供神经支配。b2c单元的肌梭运动神经支配相对简单。b2c单元的单极通常仅由一到三个轴突提供神经支配，所有轴突均以追踪分支的形式终止。在b2c单元中未发现终板末梢。这些形态学特化表明，串联肌梭中的b1b2c和b2c单元在其换能和肌梭运动机制方面均有所不同。因此，串联肌梭是一种特殊结构，可能提供超出单个肌梭所能提供的额外本体感觉信息。
