The kidney filters blood by simple Starling balance: hydrostatic pressure in the glomerular capillary (P GC) pushes plasma out into Bowman’s capsule, while the capsule’s own pressure and the plasma proteins’ oncotic pull (π GC) hold fluid in. The leftover is the net filtration pressure; GFR is that pressure times the filter’s permeability.
The clever part is the two arterioles. Because the glomerulus sits between them, squeezing the outflow (efferent) dams pressure up in the tuft and raises filtration, while squeezing the inflow (afferent) starves it and lowers filtration. Same muscle, opposite effect — that asymmetry is the whole trick.
As protein-free filtrate leaves, the remaining plasma protein concentrates, so π climbs along the capillary and filtration self-limits. And by nudging the afferent tone, the kidney holds GFR nearly constant while arterial pressure swings — autoregulation.
The simulation stopped unexpectedly — the lesson continues without it. You can move on; nothing you did was wrong.