If you could look inside a pre-synaptic axon terminal, you would find one of the characteristics is that it's loaded with these vesicles and they're just sitting there waiting to receive an action potential so that they can immediately dump their contents.

如果你能够一窥突触前的轴突末梢内部,你将会发现一个共同特征,神经递质都装载在小泡中,时刻准备着等待动作电位激活,以便迅速释放其内含物

生物医学工程探索课程节选 : 耶鲁公开课

One is that there's a physical space in between the two cells, so the axon of what's called the pre-synaptic neuron, or the neuron that's bringing a signal into the synapse, the axon terminal is physically separated from the dendrite of the next cell.

一是两个细胞间有一定的物理空间,所谓的突触前神经元,也就是将信号传递到突触的神经元的,轴突的末梢,同下一个细胞的树突间被物理性分离开

生物医学工程探索课程节选 : 耶鲁公开课