why???

When a person loses body water but most of the solute remains, such as through excessive sweating during exercise, ECF volume is decreased and osmolarity is increased;

The cell in the thirst center shrink as water moves from the cell into the hypertonic ECF;

The shrinking of these cells triggers a person's awareness of thirst and increase the urge to drink....

哈哈, 因為你那個太強大了, no shrinking, no triggers, so no thirsty feeling....