Vasoconstriction (from Latin vas 'vessel' and constringere ' constrict ') is the medical term for vascular constriction. Vasoconstriction occurs mainly through contractions of the smooth muscles in the small arteries and arterioles, mostly under the influence of the sympathetic nervous system . These blood vessels are also known as resistance vessels because they represent the peripheral resistance to blood flow. If these veins narrow, the resistance and thus also the blood pressure and the blood flow speed are increased. Ohm's and Hagen-Poiseuille's law apply . The blood flow to the tissue behind the affected vessel sections is reduced.
Local vasoconstriction and local vasodilation (expansion of the vessels) thus primarily serve to regulate blood flow to organs. The cardiac output is the quotient of blood pressure and peripheral resistance. A vasoconstriction therefore reduces the cardiac output because the resistance is in the denominator . A heart failure worsens, unless there is a compensatory to a proportional increase in blood pressure. Vasoconstrictors are considered to be drugs that increase blood pressure .
Vasoconstriction is mainly caused by hormones which bind to certain receptors in the blood vessels (e.g. in the case of noradrenaline to the α-receptors). Substances with a vasoconstrictor effect are also referred to as vasoconstrictors, vasoconstrictors, vasoconstrictors or vasoconstrictors ; together with the antagonistic acting vasodilators they form the vasoactive substances . The more pronounced atherosclerosis , the less effective it is.
Vasoconstrictor hormones are angiotensin I and II , serotonin , thromboxane A 2 , the endothelin formed by peripheral tissue cells , norepinephrine and, in very high concentrations , the otherwise vasodilatoric epinephrine .
Acute tests of strong nicotine inhalations show an almost complete vasoconstriction of the acral vessels.
In Raynaud's disease , too, there is a vasostriction of the small arteries; this is called a vasospasm .
Sympathetic efferents have a neurogenic vasoconstrictor effect, under the influence of the sympathetic the vascular base tone is increased to the resting tone : A severing of sympathetic fibers leads to reddening of the skin in the periphery due to the vasodilation.
5% of newborns in is hypothalamus located vasomotors not mature center, which is why the lack of vasoconstriction to a harlequin color change leads.
- ↑ Willibald Pschyrembel: "Clinical Dictionary" , 267th edition, de Gruyter , Berlin, Boston 2017, ISBN 978-3-11-049497-6 , page 1890.
- ↑ Christian Ebenezer: "Treatment of rheologically caused disorders of microcirculation", Mainzer Verlagsanstalt, Mainz 1990, ISBN 3-920615-11-5 , page 12.
- ↑ Duden : "The dictionary of medical technical expressions" , 4th edition, Bibliographisches Institut , Mannheim 1985, ISBN 3-411-02426-7 , page 710.
- ^ Gustav Kuschinsky , Heinz Lüllmann : "Short textbook of pharmacology" , 9th edition, Georg Thieme Verlag , 1981, ISBN 3-13-368509-0 , pages 89 f.
- ^ Hubert Mörl: "Vascular Diseases in Practice" , 2nd edition, Edition Medicine, Weinheim, Basel, Deerfield Beach 1984, ISBN 3-527-15096-X , page 47.
- ^ Heinz Heidrich (editor): "Raynaud's Phenomenon", TM-Verlag, Bad Oeynhausen 1979, page 61.