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Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, in particular the large arteries and small arterioles. The process is the opposite of vasodilation , the widening of blood vessels.
Vasodilation is the opposite of vasoconstriction, which is the narrowing of blood vessels. When blood vessels dilate , the flow of blood is increased due to a decrease in vascular resistance and increase in cardiac output [ further explanation needed ] .
The vascular nerves control vasodilation and vasoconstriction, which in turn lead to the control and regulation of temperature and homeostasis. Vasodilator innervation is restricted to the following sites : 1.) The vessels of the skeletal muscle are dilated by cholinergic sympathetic nerves 2.)
Vasoconstriction (i.e., decrease in the diameter of arteries and arterioles) increases resistance, whereas vasodilation (increase in diameter) decreases resistance. Blood flow and cardiac output are related to blood pressure and inversely related to vascular resistance.
Agonists of alpha-2 receptors in the vascular smooth muscle lead to vasoconstriction. However, in clinical practice drugs applied intravenously that are agonists of alpha-2 receptors such as clonidine lead to powerful vasodilation, which causes a decrease in blood pressure by presynaptic activation of the receptors in the sympathetic ganglia ...
The hunting reaction or hunting response is a process of alternating vasoconstriction and vasodilation in extremities exposed to cold. The term Lewis reaction is used too, named after Thomas Lewis, who first described the effect in 1930. [1] Vasoconstriction occurs first to reduce heat loss, but also results in strong cooling of the extremities.
Both of these factors affect pH and, in turn, the balance between vasodilation versus vasoconstriction in the brain. [3] [4] So, the blood vessels found specifically in the brain respond changes in dissolved carbon dioxide levels. Coronary (heart) circulation is controlled at the local level primarily by metabolic control mechanism. More ...
Vasodilation and vasoconstriction are complex phenomena; they are functions not merely of the fluid mechanics of pressure and tissue elasticity but also of active homeostatic regulation with hormones and cell signaling, in which the body produces endogenous vasodilators and vasoconstrictors to modify its vessels' compliance.