Détail de la notice
Titre du Document
Muscle fiber and motor unit behavior in the longest human skeletal muscle
Auteur(s)
HARRIS A. John ; DUXSON Marilyn J. ; BUTLER Jane E. ; ...
Résumé
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.
Editeur
Society for Neuroscience
Identifiant
PMID : 16162934 ISSN : 0270-6474 CODEN : JNRSDS
Source
The Journal of neuroscience A. 2005, vol. 25, n° 37, pp. 8528-8533 [6 pages]
Langue
Anglais
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