Bayliss effect

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The Bayliss effect or myogenic autoregulation is a contraction reaction of blood vessels named after the British physiologist William Bayliss during the local control of the blood circulation ( autoregulation ) to keep the blood flow in an organ or tissue constant .

Explanation

If the wall expansion of a small artery or arteriole changes due to an increase in blood pressure , this is answered by a contraction of the smooth muscle cells . This reduces the radius of the blood vessel and increases the vascular resistance ( Hagen-Poiseuille's law ). When the intravascular pressure drops (from Latin intra = "inside", vas = "vessel"), the vascular muscles return to their original ("basal") tone . In this way, a constant blood flow to organs and tissues can be maintained even with strongly fluctuating blood pressure (in the range between approx. 120 and 200 mmHg ).

The molecular cause of the Bayliss effect lies in the activation of mechanosensitive receptors. These can either cause an influx of calcium from the intercellular space ( extracellular space ) into the muscle cells via cation channels or, via signal transduction cascades, cause the smooth muscles to contract independently of calcium (e.g. via Rho kinase). The calcium ions form a complex with the protein calmodulin ; this complex activates the myosin light chain kinase (MLC-K), which activates the motor protein myosin II through phosphorylation ( interconversion ) and thus enables the vascular smooth muscle cell to contract. However, a similar effect also occurs when myosin light chain phosphatase (MLCP), an enzyme that works contrary to MLKK, is inhibited by Rho kinase.

This type of circulatory regulation works completely independently of the vegetative innervation of the blood vessels. This means that the Bayliss effect is retained even if the nerves supplying the vessel are severed . Only when using an antispasmodic such. B. papaverine , the effect can be canceled by a relaxation of the vascular smooth muscle cells.

The Bayliss effect is e.g. B. detectable in the kidneys , gastrointestinal tract and brain , but not in the skin and lungs .

See also

Individual evidence

  1. ^ WM Bayliss: On the local reactions of the arterial wall to changes of internal pressure. In: The Journal of Physiology 28, 1902, pp. 220-231. PMC 1540533 (free full text)