Motor-Unit Architecture in Long Parallel-Fibered Muscles

描述(申请人提供)：这项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协调的方式是肌肉产生力量和运动的能力的重要决定因素。这项提议的重点是研究人体长纤维肌肉中运动单位的组织和协调。这些肌肉中的纤维通常被认为横跨肌肉的整个长度。然而，初步研究支持这样一种观点，即一些肌肉，包括臂尺肌，可能有一个复杂的结构，由较短的纤维阵列串联排列在较长纤维的支架上。一些较长的纤维在远隔开的终板区接受来自多个运动神经元的神经支配。串联纤维如何组织成运动单元，以及这些运动单元如何协调才能有效地将力传递到肌腱，这些都是未知的。这项拟议的研究将通过以下具体目标来研究这些问题：(1)确定臂尺肌的神经支配模式；(2)确定臂尺肌中运动单位是如何组织的；(3)阐明在臂远端不同水平上协调运动单位所使用的策略；以及(4)确定多神经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学方法。在自主收缩期间，将使用多个细丝和针状电极记录肌电信号。这些信号将被分解，以识别单个运动单位的动作电位。运动单位的结构特性，包括终板位置和纤维长度，将通过分析动作电位波形来估计，运动单位的控制特性，包括招募和同步，将通过分析运动单位的放电模式来确定是否存在多神经元支配的纤维。这项拟议的工作将有助于了解特定人类肌肉的结构和功能，这将直接与几个临床应用相关，包括肌腱转移和重建手术、功能性电刺激、神经和运动学肌电图，以及治疗性锻炼。

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.