If you have ever been in a hot tub with the “jets” on, you have observed a circulating system. When the pump is “on,” the water circulates from the hot tub, through pipes, into a pump, and then back to the hot tub. In this way, the water can be put through a filter to remove impurities and be re-utilized again and again. A hot tub with its pump “on” is a simple circulatory system. When the pump is “off,” the water stops circulating and stays wherever it is in the system.
Beta blockers decrease the effect of adrenaline on the cardiovascular system, slow the heart rate, and reduce stress on the heart and the arteries. Side effects include worsening shortness of breath if you have chronic obstructive pulmonary disease or asthma; sexual dysfunction; fatigue; depression; and worsening of symptoms if you have peripheral artery disease. Beta-blocker examples include: 
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