Myogenic mechanism

Myogenic response refers to a contraction initiated by the myocyte itself instead of an outside occurrence or stimulus such as nerve innervation.

Most often observed in (although not necessarily restricted to) smaller resistance arteries, this 'basal' myogenic tone may be useful in the regulation of organ blood flow and peripheral resistance, as it positions a vessel in a preconstricted state that allows other factors to induce additional constriction or dilation to increase or decrease blood flow.

However, with the aid of the myogenic mechanism, the glomerular filtration rate remains very insensitive to changes in human blood pressure.

Model and experimental studies were performed to evaluate two mechanisms in the kidney, myogenic response and tubuloglomerular feedback.

A mathematical model showed good autoregulation through a myogenic response, aimed at maintaining a constant wall tension in each segment of the preglomerular vessels.

This finding was supported by micropuncture measurements of pressure in the terminal interlobular arteries.

Evidence that the mechanism was myogenic was obtained by exposing the kidney to a subatmospheric pressure of 40 mmHg; this led to an immediate increase in renal resistance, which could not be prevented by denervation or various blocking agents.

The contracted state of the smooth muscle depends on the grade of stretch and plays an important part in the regulation of blood flow.

The resulting influx of Ca2+ ions lead to the initiation of excitation-contraction coupling and thus contraction of the myocyte.