Then, when some stimulus causes the sodium channels open up, the sodium ions flood back in, which raises the membrane potential until it reaches its threshold.

然后，当一些刺激导致钠通道打开时，钠离子会涌入，这会提高膜电位，直到达到阈值。

That process started by depolarizing the cell — that is, pushing the cell's membrane potential from negative toward positive, past a threshold that triggered voltage-gated ion channels to open.

这个过程是从细胞去极化开始的——也就是说，将细胞膜电位从负极推高到正极，超过了触发电压门控离子通道打开的阈值。