Control of extracellular fluid: kidney mechanisms

Extracellular fluid volume is determined primarily by the balance between water and salt intake and outlet. In many cases, the amount of salt and fluid absorbed is determined by a person's habits rather than physiological control mechanisms. Because of this, the burden of extracellular volume regulation is often placed on the shoulders of the kidneys, with the kidneys having to adjust their salt and water excretion to match salt and water intake under steady-state conditions. When discussing extracellular fluid volume regulation, consider factors that regulate the amount of sodium chloride in extracellular fluid because changes in the sodium chloride content in extracellular fluid often cause parallel changes in volume. extracellular fluid provided that it is an antidiuretic hormone (ADH) - the first mechanism is at work. When the ADH thirst mechanism works normally,