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Vasodilation is the result of relaxation in smooth muscle surrounding the blood vessels. This relaxation, in turn, relies on removing the stimulus for contraction, which depends on intracellular calcium ion concentrations and is tightly linked with phosphorylation of the light chain of the contractile protein myosin .
When renal blood flow is reduced (indicating hypotension) or there is a decrease in sodium or chloride ion concentration, the macula densa of the distal tubule releases prostaglandins (mainly PGI2 and PGE2) and nitric oxide, which cause the juxtaglomerular cells lining the afferent arterioles to release renin, activating the renin–angiotensin–aldosterone system, to increase blood pressure ...
Flow-mediated dilation (FMD) refers to dilation (widening) of an artery when blood flow increases in that artery. [1] [2] The primary cause of FMD is release of nitric oxide by endothelial cells. [1] To determine FMD, brachial artery dilation following a transient period of forearm ischemia is measured using ultrasound. [3]
First, metabolites that are produced by active muscle use can alter skeletal muscle tone. Second, skeletal muscle can undergo hyperemia, which is a mechanism of local blood flow regulation with two major subtypes. Regardless of the subtype, the result of hyperemia is an increase in blood flow to the affected skeletal muscle. [4]
An arteriole is a small-diameter blood vessel in the microcirculation that extends and branches out from an artery and leads to capillaries. [ 1 ] Arterioles have muscular walls (usually only one to two layers of smooth muscle cells ) and are the primary site of vascular resistance .
Functional hyperaemia is an increase in blood flow to a tissue due to the presence of metabolites and a change in general conditions. When a tissue increases its activity, there is a well-characterized fall in the partial pressure of oxygen and pH, along with an increase in partial pressure of carbon dioxide, and a rise in temperature and the concentration of potassium ions.
Chronic venous insufficiency occurs when veins cannot pump enough blood back to the heart. [16] It results when the vein dilates secondary to a vein wall disease or when normal functioning of the valves, which serve to keep blood flowing to the heart and to prevent reflux, become damaged and/or incompetent (the dilation of a vein will prevent ...
Differences in vascular permeability between normal tissue and a tumor. Vascular permeability, often in the form of capillary permeability or microvascular permeability, characterizes the capacity of a blood vessel wall to allow for the flow of small molecules (drugs, nutrients, water, ions) or even whole cells (lymphocytes on their way to the site of inflammation) in and out of the vessel.