ANATOMY AND INNERVATION RATIOS IN MOTOR UNITS OF CAT GASTROCNEMIUS
ANATOMY AND INNERVATION RATIOS IN MOTOR UNITS OF CAT GASTROCNEMIUS
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DOI：
10.1113/jphysiol.1973.sp010370
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发表时间：
1973-01-01
影响因子：
5.5
通讯作者：
TSAIRIS, P
中科院分区：
文献类型：
--
作者：
BURKE, RE;TSAIRIS, P
1.在猫腓肠肌内侧和外侧的冰冻切片中研究了属于确定类型的单个运动单位的肌纤维。重建的纤维在个别单位的分布表明，所有三种生理类型的猫内侧腓肠肌的领土是相当广泛的。在其领土内，属于研究单位的纤维或多或少均匀分布，没有局部收集。单位纤维的密度表明，在猫内侧腓肠肌中，肌肉的给定区域可能由多达50个不同的肌肉单位共享。直接确定已识别肌肉单位的神经支配比率需要完整重建整个内侧腓肠肌内单位纤维的三维分布。两台FF型和一台FR型机组均取得了满意的效果.间接估计的平均神经支配比率预期不同的生理类型的肌肉单位获得使用的肌纤维计数与特征组织化学配置文件和数据的相对频率的运动单位的已知类型的内侧腓肠肌单位池。这种间接估计的神经支配比率同意的结果，直接纤维计数在确定的单位类型FF和FR肌肉单位。总之，现有的证据表明，猫腓肠肌内侧的平均肌肉单位包含400至800个肌纤维，无论生理类型如何。单个肌肉单位产生的张力取决于许多因素，包括神经支配比率，单位纤维的横截面积和单位纤维的特定张力输出。结果表明，腓肠肌S型单位肌纤维的比张力输出（约0.6kg/cm ~ 2）明显小于FF型单位（约1.5 ~ 2.0kg/cm ~ 2）和FR型单位（约2.6 ~ 2.9kg/cm ~ 2）。
1. Muscle fibres belonging to single motor units of identified type were studied in frozen sections of cat medial and lateral gastrocnemius muscles. Reconstruction of the distribution of fibres in individual units showed that the territories of all three physiological types present in the cat medial gastrocnemius were quite extensive. Within its territory, fibres belonging to the studied unit were distributed more or less uniformly without localized collections. The density of unit fibres suggests that, in cat medial gastrocnemius, a given region of the muscle may be shared by as many as fifty different muscle units.2. Direct determination of innervation ratios in identified muscle units required complete reconstruction of the three‐dimensional distribution of unit fibres within the whole medial gastrocnemius. Satisfactory results were obtained with two type FF units and one type FR unit.3. Indirect estimates of the average innervation ratios expected for muscle units of different physiological type were obtained using counts of muscle fibres with characteristic histochemical profiles and data on relative frequencies of motor units of known type in the medial gastrocnemius unit pool. Such indirect estimates of innervation ratios agreed with the results of direct fibre counts in identified units for types FF and FR muscle units. Taken in sum, the available evidence suggests that an average muscle unit in the cat medial gastrocnemius contains between 400 and 800 muscle fibres, irrespective of physiological type.4. Tension production by single muscle units depends on a number of factors, including innervation ratio, the cross‐sectional areas of unit fibres and the specific tension outputs of the unit fibres. The present results suggest that the specific tension output of gastrocnemius type S unit muscle fibres is considerably smaller (about 0·6 kg/cm2) than in either FF units (about 1·5–2·0 kg/cm2) or type FR units (2·6–2·9 kg/cm2).