Comparative terrestrial locomotion physiology

这项研究计划的长期目标是确定陆生哺乳动物的身体大小对运动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率之间存在一种折衷，随着身体尺寸的增加，这种折衷变得更加尖锐，从而导致运动背后的生理机制发生尺寸依赖性变化。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。最大化反应性对于最小化启动运动所需的时间和保持反馈通路的稳定性非常重要。分辨力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。最大化分辨率对于准确地感测身体的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折衷在外周神经束中表现为轴突直径之间的权衡，因此反射潜伏期和轴突总数。拟议中的研究测试了这种理论的存在和影响，因为它适用于外周神经，脊髓反射通路和运动性能，并且在很大的尺寸范围内-从鼩 鼱到大象。我的第一个目标是使用解剖技术来确定身体大小对周围神经束尺寸以及周围神经束内轴突的直径和总数的影响。目的2：利用电生理学方法研究体型对周围神经传导速度和反射潜伏期的影响。目标3使用数学建模来深入了解生物力学和脊髓反射的大小依赖性变化对四足运动稳定性的影响。结果将为神经肌肉控制系统的组织和功能提供基本见解。

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.