What is blood pressure?
- Blood pressure is a measure of the force of blood pushing outwards on your arterial walls.
- It is written as 2 numbers, such as 120/80 mm Hg.
- Optimal blood pressure is less than 120 mm Hg systolic and 80 mm Hg diastolic.
Blood pressure is typically recorded with two numbers, written as a ratio:
- Systolic: The top number, which is also the higher of the two numbers, measures pressure in the arteries when the heart beats (when the heart muscle contracts).
- Diastolic: The bottom number, which is also the lower of the two numbers, measures pressure in the arteries between heartbeats (when the heart muscle is resting between beats and refilling with blood).
Blood pressure is determined by the:
- Amount of blood the heart pumps
- Condition of the heart valves
- Pulse rate
- Pumping power of the heart
- Size and condition of the arteries
Other factors which also affect blood pressure:
- Condition of kidneys, nervous system, and/or blood vessels
- Genetics
- Foods eaten, weight, and other body-related variables
- Levels of various hormones in the body
- Volume of water in the body
The cardiovascular system regulates blood pressure in various ways:
- Specific hormones and autonomic nerve signals from the brain affect the rate and strength of heart contractions. Greater contractile force and heart rate lead to an increase in blood pressure.
- Blood vessels can affect blood pressure:
- Vasoconstriction decreases an artery’s diameter by contracting smooth muscle in the arterial wall. The sympathetic (fight or flight) division of the autonomic nervous system causes vasoconstriction, which leads to increases in blood pressure and decreases in blood flow in the constricted region.
- Vasodilation is the expansion of an artery as smooth muscle in the arterial wall relaxes after a fight-or-flight response wears off or under the effect of certain hormones or chemicals in the blood.
- Blood volume in the body affects blood pressure: A higher volume of blood in the body raises blood pressure by increasing the amount of blood pumped by each heartbeat.
- Thicker, more viscous blood from clotting disorders can raise blood pressure.
High blood pressure: This occurs when pressure in your arteries is elevated
- Essential hypertension has no obvious cause.
- Secondary hypertension occurs due to another disorder.
- Drug-induced hypertension is a form of secondary hypertension caused by a response to a medication, supplement, or other chemical substance.
Blood pressure categories:
Systolic Diastolic
- Normal (optimal) <120 <80
- Prehypertension 120-139 80-89
- Hypertension >139 >89
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