Maintaining steady blood flow to all of the organs of your body is essential, and it requires constant adjustments by your cardiovascular system. When you’re walking or running, for example, more blood than usual is required in your legs, so your heart rate and cardiac output go up. The arteries leading to the legs dilate and their capillary beds open, delivering more blood to the working muscles. When you eat, the arteries leading to the stomach and intestines dilate in a similar manner, providing additional blood needed for digestion and nutrient absorption. Likewise, when you jump out of bed in the morning, the heart must work harder and blood pressure must increase to deliver blood and oxygen to the brain. Throughout the day and night, your arteries continuously guide the rivers of blood to where they’re needed most. And constant automatic adjustments in your blood pressure, which require the coordination of your nervous system, endocrine system, and kidneys, are made all the while.
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