Understanding how axons fail is critical to preventing brain injury. From stretch experiments, we know how axons respond to forces on the time scales of milliseconds and days. Yet, there is no mechanical model that explains the behavior of the axon at both short and long time scales. Here we propose a constitutive model to study the limits of stretch-mediated axonal disconnection at different time scales. Our model combines viscoelasticity using a neo-Hookean standard linear solid and growth using stress-mediated accelerated elongation. By limiting peak and average membrane tensions, our model predicts critical elongations and elongation rates. Interestingly, the critical elongation rate is not constant, but increases after an acclimation period. Combining viscoelasticity and growth is essential to simulate axonal disconnection in stretch-mediated growth at both short and long time scales. Our model can help optimize axonal stretch experiments and provides insight into the interacting time scales within the axon.

中文翻译：

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轴突的粘弹性限制了拉伸介导的生长

了解轴突如何失效对于预防脑损伤至关重要。从拉伸实验中，我们知道轴突如何响应毫秒和天的时间尺度上的力。然而，没有机械模型可以解释轴突在短期和长期的行为。在这里，我们提出了一个本构模型来研究不同时间尺度上拉伸介导的轴突断开的限制。我们的模型结合了使用新胡克标准线性实体的粘弹性和使用应力介导的加速伸长的增长。通过限制峰值和平均膜张力，我们的模型预测临界伸长率和伸长率。有趣的是，临界伸长率不是恒定的，而是在适应期后增加。结合粘弹性和生长对于在短期和长期尺度上模拟拉伸介导的生长中的轴突断开至关重要。我们的模型可以帮助优化轴突拉伸实验，并提供对轴突内相互作用时间尺度的洞察。