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在颅骨的底都有个大洞,和一条长长的隧道相连。我们沿着隧道向下滑行,但是太困难了,因为有一条连着脑的发亮的“索链”充满了隧道的空间。这条“索链”就是斯蒂文的脊髓。脊髓是由一大捆神经细胞和神经纤维组成,它和脑一起构成了斯蒂文的中枢神经系统。沿着脊髓分布的神经纤维让斯蒂文的脑和躯体能够快速地交换信息。感觉神经将信号送达斯蒂文的脑,告诉他各种感觉;是冷还是热呀;四肢处于什么位置呢;手指头被扎了啊;脚趾好痒呀。甚至一些很特别的感觉,比如膀胱满了)!运动神经将脑的指令送回斯蒂文的肌肉和器官。斯蒂文的脊髓非常的精致,哪怕是对脊髓最轻微的损坏也足以使斯蒂文残疾。所以,脊髓被骨骼很好地保护起来,许多的骨质环状结构将脊髓藏在里面,组成了脊柱。
There is a big hole in the bottom of the skull, connected to a long tunnel. We glided down the tunnel, but it was too difficult, because there was a shiny “cable chain” attached to the brain that filled the tunnel. This “rope chain” is Steven’s spinal cord. The spinal cord is composed of a large bundle of nerve cells and nerve fibers, which together with the brain form the central nervous system of Steven. The nerve fibers distributed along the spinal cord enable Steven’s brain and body to quickly exchange information. The sensory nerves send the signal to Steven’s brain, telling him all the sensations; whether it’s cold or hot, where the limbs are, where the fingers are tied, and itchy toes. Even some very special feelings, such as the bladder is full!) Motor nerves send brain commands back to Steven’s muscles and organs. Steven’s spinal cord is so refined that even the slightest damage to the spinal cord is enough to disrupt Steven. So, the spinal cord is well protected by the bones, and many of the bony ring structures hide the spinal cord inside, making up the spine.