Question

In terms of osmolality of blood, how are sodium levels and blood pressure are regulated?

Answer 1

Osmolality measures the amount of solutes present in blood. When osmolality is high, it means electrolytes (mainly sodium) is high in blood.

Regulation of sodium in plasma is mainly controlled by ADH in blood. When osmolality increases,that is sodium increases in blood. In this case more ADH is released so that more water is absorbed from tubules and this dilutes the blood bringing back sodium levels back to normal.

Also, increased ADH (due to increased osmolality) will increase water in blood causing high blood pressure. Thus high osmolality also increases blood pressure.

Thus to decrease both sodium concentration and blood pressure, the osmolality has to be reduced and vice versa.