<p>我们的身体分为中枢神经系统( central nervous system) ，和外围神经系统 (peripheral nervous system) 。中枢神经系统包括大脑和脊髓。中枢神经系统又有单独的神经元 neuron) ，人类的大脑平均有86 billion 神经元，具体数字会因人而异。大部分的神经元都有四个部分组成：dendrites, soma (cell body), axon, and synaptic terminals. Dendrites receive information from other neurons or sensory neurons, then it carries the information towards the soma (cell body), there will be axon potential generated, through the axon which carries information out to the synaptic terminals. There are some fiber covered axon called myelin sheath. </p><p>正文还需要学习如何翻译。</p>