Question

What happens first in response to fluid loss in the ECF? What happens next?

Answer 1

Dehydration occurs when water and salt loss is greater than intake. Water and salt depletion never occurs separately, although one or the other usually predominates.

Extracellular fluid (ECF) surrounds all body cells. Extracellular fluid has two primary components: the blood fluid (called plasma) and the interstitial fluid (IF) that surrounds all cells not in the blood. The volume contraction of extracellular fluid is directly linked to and nearly proportional to the volume contraction of blood plasma called hypovolemia. Thus, it mainly affects the circulatory system, potentially causing hypovolemic shock. ECF Deficit: When salt depletion is greater, the extracellular compartments react to the excretion of a quantity of fluid that corresponds to the amount of salt lost. After this compensation, extracellar fluid and electrolytes are balanced. Both water loss and Na+ loss are associated with a decrease in the ECF volume, which is determined by the amount of Na+ in the body and not by the Na+ concentration in the plasma.