English-Hanzi/When the muscle is elongated, the muscle spindle is stretched and its nerve activity increases

When the muscle is elongated, the muscle spindle is stretched and its nerve activity increases. This increases the activity of alpha motor neurons, causing muscle fibers to contract, thereby resisting stretching. The second group of neurons also causes opposite muscle relaxation. The reflex function keeps the muscles at a constant length. 当肌肉拉长时，肌肉纺锤被拉伸并且其神经活动增加。 这增加了α运动神经元的活性，导致肌肉纤维收缩，从而抵抗了拉伸。 第二组神经元也会引起相反的肌肉松弛。 反射功能使肌肉保持恒定的长度。