How the Body Determines and Controls Blood Pressure

The way the body determines and controls blood pressure is complex. It involves the heart, arteries, and kidneys working together. Blood pressure is affected by the following:

• How fast the heart is beating (heart rate) and how forcefully it contracts. An increase in rate or force tends to increase blood pressure.
• Whether the small arteries that carry blood to the tissues can expand (dilate) and contract (constrict). If the vessels do not readily dilate, are blocked, or are stiff, the heart must work harder to pump blood into them. And blood pressure increases.
• Whether the kidneys can remove (excrete) enough salt and water from the body. If salt and water are not excreted effectively, the amount of blood in the body (blood volume) increases. When blood volume increases, the heart has to work harder, causing blood pressure to increase.

The nervous system and certain hormones also affect blood pressure. They help regulate the heart rate, the force of the heart's contractions, and the diameter of arteries (by causing them to dilate or constrict). Some hormones affect the amount of salt and water that the kidneys excrete.

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