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