What mechanism allows the kidney to stabilize GFR despite fluctuations in blood pressure?

The mechanism that allows the kidney to stabilize the glomerular filtration rate (GFR) despite fluctuations in blood pressure is renal auto-regulation. This process involves two main mechanisms: the myogenic response and tubuloglomerular feedback.

The myogenic response refers to the ability of the smooth muscle cells in the walls of the afferent arterioles to sense changes in blood pressure. When blood pressure rises, these cells respond by constricting, which decreases the blood flow into the glomeruli and helps maintain a steady GFR. Conversely, when blood pressure drops, the smooth muscles relax, allowing for increased blood flow and stabilizing GFR.

The tubuloglomerular feedback mechanism comes into play through the feedback from the macula densa cells in the distal convoluted tubule. These cells monitor the flow and composition of the filtrate. If the flow rate is too high (indicating high GFR, often associated with high blood pressure), the macula densa cells trigger a response that leads to constriction of the afferent arteriole and reduces GFR. If the flow rate is too low, these same cells signal for dilation of the arteriole, which increases GFR.

Through these mechanisms, the kidneys can