Motor-Unit Architecture in Long Parallel-Fibered Muscles

描述（由申请人提供）：本研究的长期目标是了解不同人体肌肉中运动单位的结构和行为。运动单位是神经肌肉系统的基本功能单位。肌肉纤维组织成运动单位的方式和运动单位活动的协调方式是肌肉产生力量和运动能力的重要决定因素。这项建议的重点是调查运动单位的组织和协调长，平行纤维人体肌肉。这些肌肉中的纤维通常被认为跨越肌肉的整个长度。然而，初步的工作支持这样一种观点，即包括肱桡肌在内的一些肌肉可能具有复杂的结构，由较短纤维的阵列串联排列在较长纤维的支架上组成。一些较长的纤维接受神经支配，从一个以上的运动神经元在广泛分离的终板区。串联纤维被组织成运动单元的方式，以及这些运动单元被协调以有效地将力传递到肌腱的方式尚不清楚。本研究拟从以下几个方面探讨这些问题：（1）确定肱桡肌的神经支配模式;（2）确定肱桡肌运动单位的组织结构;（3）阐明肱桡肌近远侧不同水平运动单位的协调策略;以及（4）确定多神经元支配的纤维是否存在于其他长的平行纤维肌肉中，包括肱二头肌、缝匠肌、股薄肌和背阔肌。将使用一种新的电生理方法。将使用多个细导线和针电极记录自主收缩期间的肌电信号。信号将被分解以识别个体运动单元动作电位。将通过分析动作电位波形来估计运动单元结构特性，包括终板位置和纤维长度，将通过分析运动单元放电模式来确定运动单元控制特性，包括募集和同步，以及多神经元支配纤维的存在。拟议的工作将有助于了解特定人体肌肉的结构和功能，这将直接关系到几个临床应用，包括肌腱转移和重建手术，功能性电刺激，神经和运动肌电图，以及治疗运动。

DESCRIPTION (provided by applicant): The long-term goal of this research is to understand the architecture and behavior of motor units in different human muscles. The motor unit is the basic functional unit of the neuromuscular system. The way muscle fibers are organized into motor units and the way motor unit activity is coordinated are important determinants of a muscle's ability to produce force and movement. The focus of this proposal is to investigate motor-unit organization and coordination in long, parallel-fibered human muscles. The fibers in these muscles are often assumed to span the entire length of the muscle. However, preliminary work supports the idea that some muscles, including brachioradialis, may instead have a complex architecture, consisting of arrays of shorter fibers arranged in series over a scaffolding of longer fibers. Some of the longer fibers receive innervation from more than one motoneuron at widely separated endplate zones. The way in which in-series fibers are organized into motor units, and the way these motor units are coordinated to transfer force effectively to the tendon are not known. The proposed study will investigate these issues through the following specific aims: (1) determining the innervation pattern in brachioradialis; (2) determining how motor units in brachioradialis are organized; (3) elucidating the strategy used to coordinate motor units at different proximodistal levels in brachioradialis; and (4) determining whether polyneuronally innervated fibers exist in other long, parallel-fibered muscles, including brachial biceps, sartorius, gracilis, and latissimus dorsi. A novel electrophysiological approach will be used. Electromyographic signals will be recorded during voluntary contractions using multiple fine-wire and needle electrodes. The signals will be decomposed to identify individual motor-unit action potentials. Motor-unit architectural properties, including endplate locations and fiber lengths, will be estimated by analyzing the action-potential waveforms, Motor-unit control properties, including recruitment and synchronization, and the existence of polyneuronally innervated fibers will be determined by analyzing the motor-unit discharge patterns. The proposed work will contribute knowledge about the structure and function of particular human muscles which will be directly relevant to several clinical applications, including tendon-transfer and reconstructive surgery, functional electrical stimulation, neurological and kinesiological electromyography, and therapeutic exercise.