Merck Manual

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High Blood Pressure
High Blood Pressure
High Blood Pressure

The heart is a beating muscle that pumps blood to the body through a network of arteries. The force of the blood is constantly putting pressure on the inside walls of blood vessels. This is known as “blood pressure”. Blood pressure is measured to evaluate the force and amount of blood being pumped from the heart, as well as the flexibility and condition of the vessels. Many different factors can affect blood pressure including

  • The levels of hormones in the body

  • Water and salt content

  • The condition of the heart, kidneys, nervous system, and blood vessels

Blood pressure is closely regulated by chemicals in the body that change the diameter of the blood vessels depending on the needs of the body: widening to let more blood flow or narrowing to allow less blood to flow. For example, norepinephrine is a hormone that causes blood vessel narrowing. Norepinephrine is released from the adrenal gland where it circulates in the bloodstream and binds to proteins, called alpha-adrenergic receptors, on the surface of smooth muscles within the blood vessels. Once bound, the smooth muscle cells tighten, decreasing the width of the blood vessel. Stimulation of these alpha receptors can result in blood pressure elevation.

Hypertension, or high blood pressure, is a condition where blood pressure remains abnormally high. If left untreated, hypertension can seriously damage the heart and blood vessels by adding to their workload. This can result in congestive heart failure, stroke, heart attack, kidney damage, aneurysms, or even death. Many factors can cause blood pressure to remain elevated, specifically conditions that cause narrowing of blood vessels.

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High Blood Pressure