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All organisms have mechanisms to respond to osmotic shock, with sensors and signal transduction networks providing information to the cell about the osmolarity of its surroundings; [2] these signals activate responses to deal with extreme conditions. [3]
Osmotic concentration, formerly known as osmolarity, [1] is the measure of solute concentration, defined as the number of osmoles (Osm) of solute per litre (L) of solution (osmol/L or Osm/L). The osmolarity of a solution is usually expressed as Osm/L (pronounced "osmolar"), in the same way that the molarity of a solution is expressed as "M ...
The laboratory value measures the freezing point depression, properly called osmolality while the calculated value is given in units of osmolarity. Even though these values are presented in different units, when there is a small amount of solute compared to total volume of solution, the absolute values of osmolality vs. osmolarity are very close.
Osm a = Body osmolarity after loss; V ICF b = Intracellular fluid volume before fluid loss (approximately 40% of body weight, or subtracting ECF from TBW) Osm b = Body osmolarity before loss (almost equal to plasma osmolality of 275-299 milli-osmoles per kilogram [4]) n lost K+ = Amount of substance of lost potassium; In homologous manner:
Osmoregulation is the active regulation of the osmotic pressure of an organism's body fluids, detected by osmoreceptors, to maintain the homeostasis of the organism's water content; that is, it maintains the fluid balance and the concentration of electrolytes (salts in solution which in this case is represented by body fluid) to keep the body fluids from becoming too diluted or concentrated.
This is due to urea entering the cell down its concentration gradient, followed by water. The osmolarity of normal saline, 9 grams NaCl dissolved in water to a total volume of one liter, is a close approximation to the osmolarity of NaCl in blood (about 290 mOsm/L). Thus, normal saline is almost isotonic to blood plasma.
For liquid solutions, the osmotic coefficient is often used to calculate the salt activity coefficient from the solvent activity, or vice versa. For example, freezing point depression measurements, or measurements of deviations from ideality for other colligative properties, allows calculation of the salt activity coefficient through the osmotic coefficient.
Hypoosmolar hyponatremia is a condition where hyponatremia is associated with a low plasma osmolality. [1] The term "hypotonic hyponatremia" is also sometimes used.[2]When the plasma osmolarity is low, the extracellular fluid volume status may be in one of three states: low volume, normal volume, or high volume.