Flow chart describing how humans maintain homeostatis with respect to water and ions

Decrease in Water Consumption: when a human being drinks less water, normally there will be a drop in blood volume. This will trigger hypovolemic thirst which is the way of the brain to make a person to drink more water. The kidney then releases a hormone called renin into the blood system which activates another hormone called angiotensis II which causes the blood vessels to constrict causing an increase in the blood pressure.

When excessive sodium is ingested after periods of exercise. When a human being ingests a lot of salt, after periods of exercises, these salts dissolve in the water in the body. This salt then either comes out through urine especially if it was taken to the kidney, or it could come out as sweat after the exercise, creating a balance.