The nitric oxide diffuses into the nearby smooth muscle cells, and activates guanylate cyclase, which converts GTP molecules to cGMP.

一氧化氮扩散到附近的平滑肌细胞，激活鸟苷酸环化酶，将GTP分子转化为cGMP。

Next there's the tunica media or middle tunic which is mostly made of smooth muscle cells and sheets of elastin protein.

接下来是血管中膜，主要由平滑肌细胞和弹性蛋白组成。

Second, they promote the proliferation of the smooth muscle cells in the vessel wall, which makes the vessel wall thicker and stronger.

第二，它们促使血管壁平滑肌增生，使血管壁变厚变强。

Surrounding the tunica intima is the middle layer, the tunica media, made of smooth muscle cells and sheets of the protein elastin.

围绕内膜的是中间层，中膜，由平滑肌细胞和蛋白质弹性蛋白片组成。

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。

It also builds up in the capillaries causing the basement membrane to thicken which makes it harder for oxygen to efficiently move from the vascular space to the tissues, causing hypoxia and death of the smooth muscle cells.

它还聚集在毛细血管中，使基底膜变厚，造成氧气更难从血管间隙高效地转移到组织中，导致缺氧、平滑肌细胞死亡。