Figure 63

Mechanism of autoregulation of glomerular capillary pressure in a single glomerulus from a normal kidney. A, Baseline. B, Increased perfusion pressure. Glomerular pressure is determined by three factors: mean arterial pressure (MAP) or perfusion pressure, and the relative resistance of both the afferent and efferent arterioles. The initial response to an increase in MAP is an increase in afferent arteriolar resistance (RA), preventing transmission of the elevated systemic pressure to the glomerular capillaries. Efferent arteriolar resistance (Rg) also may decline. This decrease decompresses the glomerulus, helping to limit the increase in glomerular capillary hydraulic pressure (Pqc), and maintains constant renal plasma flow.

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