INTRAMUSCULAR BRANCHING OF FUSIMOTOR FIBRES
INTRAMUSCULAR BRANCHING OF FUSIMOTOR FIBRES
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DOI：
10.1113/jphysiol.1965.sp007592
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发表时间：
1965-01-01
影响因子：
5.5
通讯作者：
BARKER, D
中科院分区：
文献类型：
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作者：
ADAL, MN;BARKER, D
在锇酸染色标本中，追踪了3只猫去传入神经的后肢中18个肌梭的28条γ运动纤维中的27条在肌肉内的走行，直至其进入3块第一蚓状肌和2块第二蚓状肌的肌梭入口处。γ纤维在肌肉内分支的特点是，它们并不按照其主干直径和髓鞘化程度为肌梭提供β₁和β₂纤维。在追踪到的18条髓鞘较厚的β主干纤维（4.0 - 7.5μm）中，7条分支后只产生β₁纤维（3.0 - 4.5μm），2条只产生β₂纤维（2.0 - 2.5μm），9条产生两者的混合纤维（所有测量值均指总直径）。追踪到的5条髓鞘较薄的β主干纤维（2.5 - 3.5μm）在肌肉内走行过程中完全没有分支；每条仅供应一个肌梭，其中3条以β₁纤维进入，2条以β₂纤维进入。在所研究的一块肌肉的肌梭运动神经供应中没有小的β主干纤维。18个肌梭中只有4个同时由大的和小的β主干纤维支配。追踪到的运动纤维中有5条既支配梭外肌纤维又支配梭内肌纤维。这些混合纤维的主干直径范围为6.0 - 12.5μm，在这两个极端情况下，它们的分布分别从主要是肌梭运动纤维到主要是骨骼肌运动纤维不等。猫的第一深蚓状肌的骨骼肌运动神经支配比例经计算为1∶300。肌梭运动神经支配比例经计算为1条β纤维或混合纤维对9个梭内肌纤维极；这些极位于1 - 5个肌梭中，通常在2个肌梭中。对动态和静态肌梭运动纤维的鉴别进行了讨论。
In teased, osmium tetroxide preparations the intramuscular course of 27 out of 28 stem motor fibres supplying 18 spindles was traced to the level of spindle entry in 3 1st and two 2nd deep lumbrical muscles removed from the de-afferentated hind limbs of 3 cats. The nature of the intramuscular branching of the y fibres was such that they did not supply [UPSILON]1 and [UPSILON]2 fibres to the spindles in accordance with their stem diameters and degree of myelination. Of 18 thickly myelinated [UPSILON]-stem fibres traced (4.0-7.5 [mu]), seven branched so as to produce [UPSILON]1 fibres only (3.0-4.5 [mu]), 2 produced [UPSILON]2 fibres only (2.0-2.5 [mu]) and 9 produced a mixture of both (all measurements refer to total diameters). Five thinly myelinated [UPSILON]-stem fibres traced (2.5-3.5 [mu]) did not branch at all in their intramuscular course; each supplied one spindle only, 3 entering as [UPSILON]1 fibres, 2 as [UPSILON]2 fibres. Small [UPSILON]-stem fibres were absent in the fusimotor supply to one of the muscles studied. Only 4 of 18 spindles were innervated by both large and small [UPSILON]-stem fibres. Five of the motor fibres traced innervated both extra- and intrafusal muscle fibres. The stem diameter of these mixed fibres ranged from 6.0 to 12.5 [mu], and at these 2 extremes their distribution varied from being predominantly fusimotor to predominantly skeletomotor, respectively. The skeletomotor innervation ratio for the cat''s 1st deep lumbrical muscle is calculated to be 1:300. The fusimotor innervation ratio is calculated to be one [UPSILON] or mixed fibre to nine intrafusal muscle-fibre poles; these are located in from one to 5 spindles, usually in 2. The identify of dynamic and static fusimotor fibres is discussed.