How does the osmolarity of the blood affect the cellular level?
Osmolarity is the amount of a solute relative to another solution. Blood osmolarity is usually determined by things like sodium, urea, and glucose. Sodium and glucose are both hormonally controlled; sodium is controlled via aldosterone and antidiuretic hormone, and glucose by insulin and glucagon. If the osmolarity of the blood is higher than that of the tissues, it will naturally draw water out of the cells and into the blood, since water follows higher solute concentrations in an effort to equalize concentration levels between tissue and blood. When this happens, it can be seen through things like increased blood pressure, increased urination, etc.
