Comparative terrestrial locomotion physiology

本研究计划的长期目标是确定体型对陆生哺乳动物运动的神经肌肉控制的影响。我的一般假设是，感觉运动系统的反应性和分辨力之间存在一种妥协，这种妥协随着体型的增加而变得更加尖锐，从而导致运动背后的生理机制的尺寸依赖性变化。反应性是指神经系统识别感官刺激并产生适当反应所需的时间。最大限度地提高反应能力对于最大限度地减少启动运动所需的时间和保持反馈路径的稳定性是很重要的。分辨是指感觉系统区分感觉刺激的能力和运动系统产生精细分级反应的能力。最大限度地提高分辨率对于准确地感知身体状态和产生适当的肌肉力量是重要的。感觉运动反应性和分辨率之间的妥协在周围神经束中表现为轴突直径、反射潜伏期和轴突总数之间的权衡。拟议的研究测试了这一理论组成的存在和含义，因为它适用于周围神经、脊髓反射通路和运动表现，并在从鼩鼱到大象的广泛尺寸范围内进行了测试。我的第一个目标是利用解剖学技术来确定体型对周围神经束尺寸的影响，以及周围神经束内轴突的直径和总数。目的2利用电生理学来确定体型对周围神经传导速度和反射潜伏期的影响。目的3使用数学模型来深入了解生物力学和脊柱反射的大小依赖性变化对四足运动稳定性的影响。这些结果将为神经肌肉控制系统的组织和功能提供基本的见解。

The long-term objective of this research program is to determine the effect of body size on the neuromuscular control of locomotion in terrestrial mammals. My general hypothesis is that there is a compromise between the responsiveness and resolution of sensorimotor systems that becomes more acute with increases in body size thereby causing size-dependent changes in the physiological mechanisms that underlie movement. Responsiveness refers to the time required for the nervous system to recognize sensory stimuli and generate an appropriate response. Maximizing responsiveness is important for minimizing the time required to initiate a movement and for maintaining stability in feedback pathways. Resolution refers to the ability of the sensory system to distinguish between sensory stimuli and to the ability of the motor system to generate finely graded responses. Maximizing resolution is important for accurately sensing the state of the body and for generating appropriate muscle forces. The compromise between sensorimotor responsiveness and resolution manifests itself in peripheral nerve bundles as a trade-off between axon diameters, and thus reflex latency, and total number of axons. The proposed research tests the presence and implications of this theoretical comprise as it applies to peripheral nerves, spinal reflex pathways, and locomotor performance and does so across a wide size range--from shrews to elephants. My first aim uses anatomical techniques to determine the effect of body size on peripheral nerve bundle dimensions as well as the diameters and total number of axons within peripheral nerve bundles. Aim 2 uses electrophysiology to determine the effect of body size on peripheral nerve conduction velocity and reflex latency. Aim 3 uses mathematical modeling to gain insight into the effect of size-dependent changes in biomechanics and spinal reflexes on the stability of quadrupedal locomotion. The results will provide fundamental insight into the organization and function of neuromuscular control systems.