为了保存肌肉所需要的血液，皮肤血管收缩，而肌肉血管舒张。
To conserve blood that will be needed by muscles, skin vessels constrict while vessels of the muscles dilate.
血压：血液作用于血管壁的压力，产生于心脏的泵推作用。血管的舒张和收缩对维持血液的流动有所帮助。
Blood pressure: Force originating when the heart's pumping pushes the Blood against the walls of the Blood vessels. Their stretching and contraction help maintain Blood flow.
较大剂量时，也能舒张外周阻力血管和心肌阻力血管从而降低血压，还可以间接地增强心肌收缩力。
If large doses are used, they can diastole outside resistant blood vessels and myocardial resistant vessels and they can reduce blood pressure and also indirectly enhance myocardial systole.
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