The smooth muscle of the blood vessels reacts to the stretching of the muscle by opening ion channels, which cause the muscle to depolarize, leading to muscle contraction. This significantly reduces the volume of blood able to pass through the lumen, which reduces blood flow through the blood vessel. Alternatively when the smooth muscle in the blood vessel relaxes, the ion channels close, resulting in vasodilation of the blood vessel; this increases the rate of flow through the lumen.
This system is especially significant in the kidneys, where the glomerular filtration rate (the rate of blood filtration by the nephron) is particularly sensitive to changes in blood pressure. However, with the aid of the myogenic mechanism, the glomerular filtration rate remains very insensitive to changes in human blood pressure.