On the smooth muscle cells controlling some blood vessels, there are receptors called alpha receptors — when norepinephrine, or epinephrine, bind to those receptors, they make those smooth muscle cells contract, thereby restricting blood flow.

在控制一些血管的平滑肌细胞上，有一种叫做α受体的受体——当去甲肾上腺素或肾上腺素与这些受体结合时，它们使这些平滑肌细胞收缩，从而限制血液流动。

But on smooth muscle cells that control other blood vessels, there are lots of beta receptors for epinephrine and norepinephrine, and when they are activated, they make the muscles relax, letting more blood flow through.

但是在控制其他血管的平滑肌细胞上，有许多肾上腺素和去甲肾上腺素的β受体，当它们被激活时，它们使肌肉放松，让更多的血液流过。