CSF influx (periarterial)
CSF efflux (perivenous)
Waste (amyloid-β)
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The brain has no lymphatic vessels of its own, so it clears metabolic waste through a dedicated plumbing system instead: cerebrospinal fluid pumped in along the pulsating wall of a penetrating artery, exchanged with the interstitial fluid through aquaporin-4 water channels on astrocyte endfeet, and swept back out along a vein. This 2D schematic renders that periarterial-to-perivenous loop as a flat circuit diagram — a violet CSF stream flows in along the left channel, diffuses through the shaded interstitium, and drains out along the right channel, while amber waste particles (standing in for amyloid-β) have to random-walk their way to the venous drain to be cleared. A sleep/wake toggle changes the interstitial space fraction the way real astrocyte shrinkage does during sleep, a cardiac-rate slider sets the pulsatile pumping strength, and an AQP4-density slider throttles the capture step, so you can watch — on the diagram and on the live clearance-rate strip chart below it — why poor sleep and low AQP4 both stall real waste clearance.