Vasoconstriction

Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, particularly the large arteries, small arterioles and veins. The process is the opposite of vasodilation, the widening of blood vessels. The process is particularly important in staunching hemorrhage and acute blood loss.

Mechanism

When blood vessels constrict, the flow of blood is restricted or decreased, thus retaining body heat or increasing vascular resistance. This makes the skin turn paler because less blood reaches the surface, reducing the radiation of heat. On a larger level, vasoconstriction is one mechanism by which the body regulates and maintains mean arterial pressure.

Substances causing vasoconstriction are called vasoconstrictors or vasoconstrictive substances. Many vasoconstrictors also cause pupil dilation. Medications that cause vasoconstriction include: antihistamines, decongestants, and stimulants used to treat ADHD.

Clinical significance

Vasoconstriction can be a contributing factor to erectile dysfunction. The constriction of blood vessels can also cause full or partial blockage of blood flow to potentially critical organs such as the heart (causing myocardial infarction) or the brain (causing stroke).

See also

• Vasodilation
• Myogenic mechanism

References

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