Medical Questions » Blood Pressure Questions » Question No. 148
| Question: | You constantly hear about high blood pressure, but what about low blood pressure. What causes this? |
| Answer: | The level of blood pressure is due to a combination of the amount of blood present in the circulation, the force of contraction of the heart and the diameter of the blood vessels.
If you lose a large amount of blood your blood pressure will drop due to a lack of blood. If your heart contracts forcibly your blood pressure may rise excessively, but if it beats weakly it may fall.
If the arteries become dilated, as may happen with frights, sudden change in position or shock, the blood pressure may fall. If they are narrowed by hardening from excess cholesterol, or by spasm from chemical stimuli within the body, the blood pressure will rise.
The regulation of blood pressure is very complex, and numerous chemical and physical factors are involved. People with persistently low blood pressure need investigations to find out why it is low, but in many cases no apparent cause can be found. In the elderly, narrowing of arteries may restrict the blood supply to the brain, and even though their blood pressure is normal, they may feel light headed and dizzy when rising from a bed or chair. |
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