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Veins have a much higher compliance than arteries (largely due to their thinner walls.) Veins which are abnormally compliant can be associated with edema . Pressure stockings are sometimes used to externally reduce compliance, and thus keep blood from pooling in the legs.
Transmural pressure is the difference in pressure between two sides of a wall or equivalent separator. According to myogenic theory smooth muscle contract in response to increased transmural pressure and relax to decreased transmural pressure For body vasculature or other hollow organs, see Smooth muscle#External substances
Baroreceptors are integral to the body's function: Pressure changes in the blood vessels would not be detected as quickly in the absence of baroreceptors. When baroreceptors are not working, blood pressure continues to increase, but, within an hour, the blood pressure returns to normal as other blood pressure regulatory systems take over.
Low pressure baroreceptors have both circulatory and renal effects, which produce changes in hormone secretion. Stimulation of these receptors causes the atria to release atrial natriuretic peptide. This hormone acts on the kidneys to increase sodium excretion, which increases urine production and thereby leads to a decrease in blood pressure.
The blood pressure in blood vessels is traditionally expressed in millimetres of mercury (1 mmHg = 133 Pa). In the arterial system, this is usually around 120 mmHg systolic (high pressure wave due to contraction of the heart) and 80 mmHg diastolic (low pressure wave). In contrast, pressures in the venous system are constant and rarely exceed 10 ...
The main endogenous agonist of these cell receptors is norepinephrine (NE). The adrenergic receptors exert opposite physiologic effects in the vascular smooth muscle under activation: alpha-1 receptors. Under NE binding alpha-1 receptors cause vasoconstriction (contraction of the vascular smooth muscle cells decreasing the diameter of the ...
It is part of a body negative feedback loop in which the body tries to restore homeostasis (maintain constant internal environment). [citation needed] For example, vasoconstriction is a hypothermic preventative in which the blood vessels constrict and blood must move at a higher pressure to actively prevent a hypoxic reaction.
Veins have less smooth muscle and connective tissue and wider internal diameters than arteries. Because of their thinner walls and wider lumens they are able to expand and hold more blood. This greater capacity gives them the term of capacitance vessels. At any time, nearly 70% of the total volume of blood in the human body is in the veins. [3]