What causes vasoconstriction and vasodilation?
Vasodilation (definition) = the increase in the internal diameter of blood vessels that is caused by relaxation of smooth muscles within the wall of the vessels, thus causing an increase in blood flow. The opposite effect is vasoconstriction.
So in brief, regional vasoconstriction, within physiological limits, will increase blood pressure, but conversely decrease flow because blood is shunted to other lower resistance areas.
- The exact causes of high blood pressure are not known, but several things may play a role, including:
- Being overweight or obese.
- Lack of physical activity.
- Too much salt in the diet.
- Too much alcohol consumption (more than 1 to 2 drinks per day)
- Older age.
- The heart will work harder to pump the needed oxygen to the body." She says that blood viscosity can increase because of many factors, such as certain medications, too many red blood cells, high lipid levels, and other conditions, including diabetes and cancer.
- Veins operate at a lower blood pressure, since the blood has lost considerable pressure traveling through the arteries and capillaries. Therefore, veins are less muscular than arteries. Also, many veins must transport blood from the lower body up to the heart. This requires the blood to flow against gravity.
Vasodilation caused by relaxation of smooth muscle cells in arteries causes an increase in blood flow. When blood vessels dilate, the blood flow is increased due to a decrease in vascular resistance. Therefore, dilation of arteries and arterioles leads to an immediate decrease in arterial blood pressure and heart rate.
- The local vascular effects of adenosine are primarily vasodilation of the different beds. In spite of this “indirect” vasoconstrictor effect produced by caffeine, it is important to point out that the chronic consumption of caffeine creates a tolerance to its adenosine receptor-dependent effects.
- Aims Compared with other non-steroid anti-inflammatory drugs (NSAIDs), aspirin is not correlated to hypertension. It has been shown that aspirin has unique vasodilator action in vivo, offering an expla- nation for the unique blood pressure effect of aspirin.
- At intoxicating levels, alcohol is a vasodilator (it causes blood vessels to relax and widen), but at even higher levels, it becomes a vasoconstrictor, shrinking the vessels and increasing blood pressure, exacerbating such conditions as migraine headaches and frostbite.
Updated: 2nd October 2019