Muscle fiber and motor unit behavior in the longest human skeletal muscle
Muscle fiber and motor unit behavior in the longest human skeletal muscle
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DOI：
10.1523/jneurosci.0923-05.2005
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发表时间：
2005-09-14
影响因子：
5.3
通讯作者：
Gandevia, SC
中科院分区：
文献类型：
--
作者：
Harris, AJ;Duxson, MJ;Gandevia, SC
缝匠肌是人体最长的肌肉。它呈带状，长度可达 600 毫米，包含五到七个神经血管室，每个室都有一个神经肌肉终板区。它的一些纤维终止于束内，而另一些纤维可能贯穿肌肉的整个长度。为了评估这块长肌肉的运动单位内激活的位置和时间，我们记录了稳定随意收缩期间沿着缝匠肌的多个肌内电极的肌电电位，并通过插入肌肉近端附近的针状电极的尖峰触发平均值来分析它们的活动。大约 30% 的缝匠肌运动单位包括贯穿肌肉全长的肌纤维，以 3.9 +/- 0.1 m/s 的速度传导动作电位。大多数运动单位在单个肌肉终板区域内受神经支配，该区域不一定靠近纤维的中点。因此，动作电位在终板区域启动后 100 毫秒才到达单元的远端。因此，收缩活动沿着单个缝匠肌纤维的长度并不同步。我们假设，力从纤维到肌内膜的横向传递以及运动单元终板沿肌肉的广泛分布对于力从肌节到肌腱的有效传递以及防止因肌纤维非活动区域过度伸展而引起的肌肉损伤至关重要。
The sartorius muscle is the longest muscle in the human body. It is strap-like, up to 600 mm in length, and contains five to seven neurovascular compartments, each with a neuromuscular endplate zone. Some of its fibers terminate intrafascicularly, whereas others may run the full length of the muscle. To assess the location and timing of activation within motor units of this long muscle, we recorded electromyographic potentials from multiple intramuscular electrodes along sartorius muscle during steady voluntary contraction and analyzed their activity with spike-triggered averaging from a needle electrode inserted near the proximal end of the muscle. Approximately 30% of sartorius motor units included muscle fibers that ran the full length of the muscle, conducting action potentials at 3.9 +/- 0.1 m/s. Most motor units were innervated within a single muscle endplate zone that was not necessarily near the midpoint of the fiber. As a consequence, action potentials reached the distal end of a unit as late as 100 ms after initiation at an endplate zone. Thus, contractile activity is not synchronized along the length of single sartorius fibers. We postulate that lateral transmission of force from fiber to endomysium and a wide distribution of motor unit endplates along the muscle are critical for the efficient transmission of force from sarcomere to tendon and for the prevention of muscle injury caused by overextension of inactive regions of muscle fibers.