Your brain sends action potentials down your spinal cord and preganglionic neuronal axons.

你的大脑发送动作电位到你的脊髓和节前神经轴突。

In both systems, neurons release acetylcholine, or ACh, in their preganglionic synapses.

在这两个系统中，神经元在节前突触中释放乙酰胆碱。

Like all preganglionic fibers, these release acetylcholine, too.

像所有节前纤维一样，它们也释放乙酰胆碱。

So, the preganglionic fiber releases ACh, and the postganglionic releases norepinephrine.

所以节前神经纤维释放 ACh，节后神经纤维释放去甲肾上腺素。

The key here is that, in the sympathetic system, the preganglionic fibers are much shorter than the postganglionic ones.

这里的关键是，在交感神经系统中，节前纤维比节后纤维短得多。

Since parasympathetic ganglia are so close to, or even inside of, their effector organs, the preganglionic fibers are a lot longer.

由于副交感神经节如此接近其效应器官甚至在它们的内部，节前纤维要长得多。

Understandably enough, the axon lengths of the neurons before the ganglion are called the preganglionic fibers, and the ones coming out are postganglionic.

可以理解的是，神经节前神经元的轴突长度被称为节前纤维，出来的是节后纤维。