How is it possible for a human to alter their blood pressure?

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We humans have somewhat sealed loop of blood circulating around, so how are we able to alter the blood pressure without “opening” a valve somewhere or something like that to let blood out/in(imagine a pipe with a valve)? Where does the pressure come and go to?

In: Biology

Your blood vessels are not static pipes, they are living, moving, muscular tissue themselves that expand or contract based on the situation. The blood pressure raises and lowers when those vessels change sizes, or when your heart pumps harder/less hard.

Your heart is a muscle. That means it can do less work or more work, depending on the required load. Sometimes we need to fight, sometimes we need to rest, sometimes we need to run.

Our arteries and veins adapted along with the system, so they can sustain rapid changes of pressure.

The pipe in your analogy doesn’t really work because a pipe is constant in size, whereas the vessels in your circulatory system can constrict or dilate, making the blood flow through a larger or smaller circuit depending on the circumstances (consequently altering resistance to flow and pressure). In addition, your heart is a pump with variable output, increasing or decreasing the output by changing how fast it is beating and the amount of force (and therefore volume) of each beat. So although the circulatory system is essentially a closed system it can vary significantly in volume, and the pump can vary significantly in output.

You open a “valve” thousands of times per day. It’s called your “mouth.”

When you open your mouth and drink water, for example, you’re adding fluid into the system that is circulated throughout your blood stream. Blood is not 100 percent blood cells. Much of it is water.

Your kidneys act as another “valve,” by removing excess water from your system in the form of urine. Similarly, many blood pressure medications act to lower blood pressure by increasing the rate at which water is removed from your system.