Vascular Smooth Muscle

Information about Vascular Smooth Muscle

Human Vascular smooth muscle isolated from Aorta

Vascular smooth muscle refers to the particular type of smooth muscle found within, and composing the majority of the wall of blood vessels.

Vascular smooth muscle contracts or relaxes to both change the volume of blood vessels and the local blood pressure, a mechanism that is responsible to redistribution of the blood within the body to areas where it is needed (i.e. areas with temporarily enhanced oxygen consumption). Thus the main function of vascular smooth muscle tonus is to regulate the caliber of the blood vessels in the body. Excessive vasoconstriction leads to hypertension, while excessive vasodilation as in shock leads to hypotension.

Arteries have a great deal more smooth muscle within their walls than veins, thus their greater wall thickness. This is because they have to pump blood away from the heart to all the organs and tissues that need the oxygenated blood. The endothelial lining of each is similar.

Vascular smooth muscle is innervated primarily by the sympathetic nervous system through adrenergic receptors (adrenoceptors). Three types of adrenoceptors are present within vascular smooth muscle cells: $\text{[math]}$ , $\text{[math]}$ and $\text{[math]}$ . 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:

$\text{[math]}$ receptors. Under NE binding $\text{[math]}$ receptors cause vasoconstriction i.e. contraction of the vascular smooth muscle cells decreasing the diameter of the vessels. $\text{[math]}$ receptors are activated in response to shock or hypotension as a defensive reaction trying to restore the normal blood pressure. Antagonists of $\text{[math]}$ receptors (doxazosin, prazosin) cause vasodilation i.e. decrease in vascular smooth muscle tone with increase of vessel dimater and decrease of the blood pressure. (See also receptor antagonist)
$\text{[math]}$ receptors. Agonists of $\text{[math]}$ receptors in the vascular smooth muscle lead to vasoconstriction. However in clinical practice applied intravenously drugs being agonists of $\text{[math]}$ receptors (chlophazolin) leads to powerful vasodilation and decrease in the blood pressure by presynaptic activation of $\text{[math]}$ receptors in the sympathetic ganglia. This presynaptic effect is predominant and completely overrides the vasoconstrictive effect of the $\text{[math]}$ receptors in the vascular smooth muscle.
$\text{[math]}$ receptors. Agonism at $\text{[math]}$ receptors causes vasodilation and hypotension, i.e. the effect is opposite of the one resulting from activation of $\text{[math]}$ and $\text{[math]}$ receptors in the vascular smooth muscle cells. Usage of agonists of $\text{[math]}$ receptors as hypotensive agents is less widespread due to adverse effects such as unnecessary bronchodilation in lungs and increase in blood sugar levels.

Factors

Factors that trigger vasoconstriction are both of exogenous origin, i.e. medication, and as a response from the body itself.

Body mechanisms

Vasoconstriction is a procedure of the body to e.g.
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Hypertension
Classification & external resources

ICD-10 I 10. ,I 11. ,I 12. ,
I 13. ,I 15.
ICD-9 401.x

OMIM 145500
DiseasesDB 6330
MedlinePlus 000468
eMedicine med/1106 ped/1097 emerg/267

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A vasodilator is a drug or chemical that relaxes the smooth muscle in blood vessels, which causes them to dilate. Dilation of arterial blood vessels (mainly arterioles) lead to a decrease in blood pressure.
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MeSH D007022

In physiology and medicine, hypotension refers to an abnormally low blood pressure. This is best understood as a physiologic state, rather than a disease. It is often associated with shock, though not necessarily indicative of it.
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Arteries are muscular blood vessels that carry blood away from the heart.^[1] All arteries, with the exception of the pulmonary and umbilical arteries, carry oxygenated blood.

The circulatory system is extremely important for sustaining life.
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vein is a blood vessel that carries blood toward the heart. The majority of veins in the body carry low-oxygen blood from the tissues back to the heart; the exceptions being the pulmonary and umbilical veins which both carry oxygenated blood.
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endothelium is the thin layer of cells that line the interior surface of blood vessels, forming an interface between circulating blood in the lumen and the rest of the vessel wall. Endothelial cells line the entire circulatory system, from the heart to the smallest capillary.
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The Sympathetic Nervous System (SNS) is a branch of the autonomic nervous system. It is always active at a basal level (called sympathetic tone) and becomes more active during times of stress.
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adrenergic receptors (or adrenoceptors) are a class of G protein-coupled receptors that are targets of the catecholamines. Adrenergic receptors specifically bind their endogenous ligands, the catecholamines adrenaline and noradrenaline (called epinephrine and norepinephrine
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Norepinephrine (INN)(abbr. norepi or NE) or noradrenaline (BAN) is a catecholamine and a phenethylamine with chemical formula C₈H₁₁NO₃. The natural stereoisomer is L -(−)-(R)-norepinephrine.
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Vasoconstriction is a narrowing of the lumen of blood vessels.

Factors

Factors that trigger vasoconstriction are both of exogenous origin, i.e. medication, and as a response from the body itself.

Body mechanisms

Vasoconstriction is a procedure of the body to e.g.
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Doxazosin mesylate, a quinazoline compound sold by Pfizer under the brand name Cardura®, is an alpha blocker used to treat high blood pressure and benign prostatic hyperplasia.
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Prazosin, trade names Minipress® and Hypovase®, is a medication used to treat high blood pressure (hypertension). It belongs to the class of alpha-adrenergic blockers, which lower blood pressure by relaxing blood vessels.
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receptor antagonist is a drug that does not provoke a biological response itself upon binding to a receptor, but blocks or attenuates agonist-mediated responses. It may be competitive (or surmountable), i.e.
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agonist is a substance that binds to a specific receptor and triggers a response in the cell. It mimics the action of an endogenous ligand (such as hormone or neurotransmitter) that binds to the same receptor.
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Clonidine is a direct-acting adrenergic agonist prescribed historically as an anti-hypertensive agent. It has found new uses, including treatment of some types of neuropathic pain, opioid detoxification, sleep hyperhydrosis, and, off-label, to counter the side effects of stimulant
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The term mural cell refers generally to vascular smooth muscle cells and pericytes, both involved in the formation of normal vasculature and responsive to vascular endothelial growth factor (VEGF).
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Histology (from the Greek ἱστός) is the study of tissue sectioned as a thin slice, using a microtome. It can be described as microscopic anatomy.
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MUSCLE (multiple sequence comparison by log-expectation) is public domain, multiple sequence alignment software for protein and nucleotide sequences.
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Skeletal muscle is a type of striated muscle, usually attached to the skeleton. Skeletal muscles are used to create movement, by applying force to bones and joints; via contraction.
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Herod_Archelaus

• • [ e] Histology: muscle tissue
skeletal muscle/general	epimysium, fascicle, perimysium, endomysium, muscle fiber (intrafusal, extrafusal), myofibril sarcomere (a, i, and h bands; z and m lines), myofilaments (thin filament/actin, thick filament/myosin, elastic filament/titin, nebulin), tropomyosin, troponin (T, C, I) costamere (dystrophin, α,β-dystrobrevin, syncoilin, synemin/desmuslin, dysbindin, sarcoglycan, dystroglycan, sarcospan), desmin neuromuscular junction, motor unit, muscle spindle, excitation-contraction coupling, sliding filament mechanism myoblast, satellite cell, sarcoplasm, sarcolemma, sarcoplasmic reticulum, T-tubule
cardiac muscle	myocardium, intercalated disc, nebulette
smooth muscle	calmodulin, vascular smooth muscle

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Vascular Smooth Muscle

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Body mechanisms

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Body mechanisms