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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.
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.
Vascular resistance is the resistance that must be overcome for blood to flow through the circulatory system.The resistance offered by the systemic circulation is known as the systemic vascular resistance or may sometimes be called by another term total peripheral resistance, while the resistance caused by the pulmonary circulation is known as the pulmonary vascular resistance.
The normal range of GFR, adjusted for body surface area, is 100–130 average 125 (mL/min)/(1.73 m 2) in men and 90–120 (mL/min)/(1.73 m 2) in women younger than the age of 40. In children, GFR measured by inulin clearance is 110 (mL/min)/(1.73 m 2 ) until 2 years of age in both sexes, and then it progressively decreases.
The normal range of GFR, adjusted for body surface area, is 100–130 average 125 mL/min/1.73m 2 in men and 90–120 ml/min/1.73m 2 in women younger than the age of 40. In children, GFR measured by inulin clearance is 110 mL/min/1.73 m 2 until 2 years of age in both sexes, and then it progressively decreases.
Alpha 1 blockers inhibit vasoconstriction normally initiated by the baroreceptor reflex upon postural change and the subsequent drop in pressure. [26] Other antihypertensive medications may also cause orthostatic hypotension, in addition to anticholinergics , dopaminergic drugs, opiates and psychoactive medications .
Pulse pressure is calculated as the difference between the systolic blood pressure and the diastolic blood pressure. [3] [4]The systemic pulse pressure is approximately proportional to stroke volume, or the amount of blood ejected from the left ventricle during systole (pump action) and inversely proportional to the compliance (similar to elasticity) of the aorta.
In obstructive lung disease, the FEV1 is reduced due to an obstruction of air escaping from the lungs. Thus, the FEV1/FVC ratio will be reduced. [4] More specifically, according to the National Institute for Clinical Excellence, the diagnosis of COPD is made when the FEV 1 /FVC ratio is less than 0.7 or [8] the FEV 1 is less than 75% of predicted; [9] however, other authoritative bodies have ...