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Blood pressure advice A normal blood pressure is a systolic blood pressure of 120 mm Hg or lower or a diastolic pressure of 80 mmHg or lower. It is the force applied by the blood against the wall of the blood vessels. It is a function of cardiac output and the resistance of the blood vessels to the flow of blood. If the diameter of the blood vessels is decreased, resistance and pressure increases. If the diameter is increased, resistance decreases and blood pressure is lowered.
There are many systems that can maintain the blood pressure homeostatically.
One regulator is sympathetic nervous system for short term and the kidney for long term.When there is a fall in blood pressure, the sympathetic nervous system secretes norepinephrine which acts on the arteries to increase the resistance and blood pressure. The kidney can control the extra cellular fluid volume and secrete rennin which activates rennin angiotensin mechanism. If the regulation falters, hypertension can occur.
Blood pressure can vary with age, heredity, diet, obesity, and lifestyle. It is very difficult to survive in 10 to 20 blood pressure. When the pressure become low, the perfusion of the brain is decreased causing lightheadedness, dizziness and fainting.10 to 20 bp is too low for a person to sustain.
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