|With water intake, the (red→blue) negative feedback decreases the number of water channels.|
① Water intake decreases plasma osmolarity, and water reabsorption (through the water channels) decreases plasma osmolarity. These effects are in the same direction (red).
② Since these effects are in the same direction (red), negative feedback decreases (blue) the number of water channels and the water reabsorption. The plasma osmolarity-decreasing effect of the water reabsorption becomes weaker, and the plasma osmolarity returns to normal.