Myogenic mechanism

Myogenic mechanism is a physiological process that allows vascular smooth muscle to maintain a state of vascular tone independent of neural input. This mechanism is essential for the autoregulation of blood flow in certain systemic circulatory structures, particularly the renal circulation and cerebral circulation.

Mechanism

The myogenic mechanism is initiated by an increase in arterial pressure, which stretches the vascular smooth muscle cells in the walls of the arterioles. This stretch triggers an influx of calcium ions into the cells, causing them to contract and thereby increase vascular resistance. This increase in resistance reduces blood flow back to its normal level, despite the increased arterial pressure. Conversely, a decrease in arterial pressure reduces the stretch on the vascular smooth muscle cells, causing them to relax and thereby decrease vascular resistance. This decrease in resistance increases blood flow back to its normal level, despite the decreased arterial pressure.

Role in Autoregulation

The myogenic mechanism plays a crucial role in the autoregulation of blood flow in the renal and cerebral circulations. In the kidney, it helps to maintain a constant glomerular filtration rate (GFR) despite changes in systemic arterial pressure. In the brain, it helps to maintain a constant cerebral blood flow (CBF) despite changes in systemic arterial pressure.

Clinical Significance

Impairment of the myogenic mechanism can lead to pathological conditions such as hypertension, stroke, and kidney disease. For example, in hypertension, the increased arterial pressure can overwhelm the myogenic mechanism, leading to excessive vasoconstriction and reduced blood flow to the tissues. Similarly, in stroke, the decreased arterial pressure can overwhelm the myogenic mechanism, leading to excessive vasodilation and increased blood flow to the tissues, which can cause cerebral edema and brain damage.

See Also

• Autoregulation
• Vascular smooth muscle
• Renal circulation
• Cerebral circulation

References

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