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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].
In vasodilation the blood vessels dilate to allow more blood flow. The smooth muscle cells are relaxed to increase the diameter of flow, decreasing the vascular resistance. This is possible due to the direct relationship between the cardiac output, mean arterial pressure and the vascular resistance.
The vessel increases in diameter until the stress is normalized (Prior et al., 2004). Arteriogenesis does not occur every time there is an increase in flow, however. Most vessel networks can handle increased flow without significantly increasing diameter because flow increases with the square (power 2) of the vessel diameter.
During inspiration, increased lung volumes cause alveolar expansion and lengthwise stretching of the interstitial alveolar vessels. This increases their length and reduces their diameter, thus increasing alveolar vessel resistance. On the other hand, decreased lung volumes during expiration cause the extra-alveolar arteries and veins to become ...
Substances called vasoconstrictors can reduce the size of blood vessels, thereby increasing blood pressure. Vasodilators (such as nitroglycerin) increase the size of blood vessels, thereby decreasing arterial pressure. If the blood viscosity increases (gets thicker), the result is an increase in arterial pressure.
Some vasoactive chemicals such as vasodilator acetylcholine are known for causing reduced/increased blood flow in the tumours by vasomotor changes. Inadequate blood supply to the tumour cells can cause the cells to be radio-resistant and resulted in reduced accessibility to chemotherapeutic agents.
Cardiologists share the truth about when blood vessel plaque buildup becomes dangerous.
The opposite process occurs when the blood leaves the capillaries and enters the venules, where the blood pressure drops due to an increase in flow rate. Arterioles receive autonomic nervous system innervation and respond to various circulating hormones in order to regulate their diameter. Retinal vessels lack a functional sympathetic ...