Answer:
1. The decrease in the extracellular fluid upsurges the plasma osmolarity.
2. This enhanced plasma osmolarity stimulates the osmoreceptors.
3. These osmoreceptors further instigate the discharging of anti-diuretic hormone.
4. The water is reabsorbed from the renal tubules and the urine turns more concentrated when the discharging of ADH takes place.