Physiology of Fluid Balance and Homeostasis

The movement of fluid and solutes between the intracellular (ICF) and extracellular (ECF) compartments.

The concentration of solutes in a solution, determined by the number of particles per unit volume.

A measurement of the total solute concentration in the blood. It is primarily determined by the serum Na concentration and is important for regulating ICF volume.

The main regulator of blood volume.

The main regulator of serum osmolality.

A condition where the blood sodium concentration is abnormally low.

A condition where the blood sodium concentration is abnormally high.

A pump that maintains the concentration gradients of sodium and potassium across cell membranes, crucial for cell function and volume regulation.

A state where the body retains too much water, leading to hyponatremia, despite normal or even low extracellular fluid volume.

A cause of hyponatremia where the body abnormally produces or secretes AVP (vasopressin), leading to excessive water retention.

A condition where AVP (vasopressin) is released in response to low blood volume.

A situation where total sodium content in the body remains normal, but the sodium concentration in the blood is low due to elevated serum lipids or proteins.

A decrease in the effective circulating volume (ECV) of blood, despite normal total blood volume, leading to non-osmotic AVP release.

A situation where the water content in the blood is reduced, making the sodium concentration appear higher.

The movement of water across a semipermeable membrane from a region of high water concentration (low solute concentration) to a region of low water concentration (high solute concentration). This movement aims to equalize the solute concentration on both sides of the membrane.

A solution that has the same concentration of solutes as another solution, typically referring to the concentration of solutes in the body's extracellular fluid (ECF).

A solution that has a higher concentration of solutes than another solution, typically the ECF. When cells are exposed to a hypertonic solution, water moves out of the cells, causing them to shrink.

A solution that has a lower concentration of solutes than another solution, typically the ECF. When cells are exposed to a hypotonic solution, water moves into the cells, causing them to swell.

The process of red blood cells bursting due to an influx of water, typically caused by exposure to a hypotonic solution.

The shrinking of cells due to an outflow of water, typically caused by exposure to a hypertonic solution.

A hormone produced by the hypothalamus and released by the pituitary gland that helps regulate water balance in the body. It acts on the kidneys to increase water reabsorption, thus reducing urine output.

Specialized cells in the renal collecting ducts that are responsible for reabsorbing water from the filtrate back into the bloodstream. They are regulated by AVP.

A type of water channel protein that is found in the membranes of principal cells in the collecting ducts. They are inserted into the cell membrane by the action of AVP, increasing the permeability of the cell to water.

The total body water (TBW) is the amount of water in the body, measured as a percentage of body weight. It is a critical factor in maintaining fluid balance.

A diagnostic test where a patient with polyuria is deprived of water for 8-12 hours in a supervised setting to see if their body can concentrate urine properly.

A synthetic hormone similar to ADH, used to treat central diabetes insipidus (DI) and nephrogenic DI.

Diagnosing central DI involves administering desmopressin and observing a prompt increase in urine osmolality (above 600 mOsm/kg) and a decrease in urine volume.

Diagnosing nephrogenic DI involves administering desmopressin and observing no increase in urine osmolality above 300 mOsm/kg.

A condition caused by excessive sodium intake or fluid overload, leading to osmotic diuresis and increased urine volume with high osmolality (>300 mOsm/kg).

The process of correcting hypernatremia by restoring serum sodium levels (145-150 mEq/L) gradually to avoid damaging brain cells.

The process of restoring extracellular fluid (ECF) volume to normal, which may be necessary in hypernatremia treatment.

Sodium excretion is compromised in patients with organ dysfunction, leading to volume expansion during sodium overload.

A type of hypernatremia where the body's total water content is reduced, leading to increased sodium concentration in the blood.

A type of hypernatremia where the body's total water content is reduced due to excessive water loss from the body, such as through sweating, fever, or diarrhea.

A type of hypernatremia where the body's total water content is reduced due to the body's inability to retain water, often caused by conditions like diabetes insipidus or lithium use.

A type of hypernatremia where the body's total water content is increased, leading to high sodium concentration in the blood.

A type of hypernatremia caused by excessive administration of sodium-containing fluids, leading to high sodium concentration in the blood.

A type of hypernatremia where the body's total water content remains stable, but sodium concentration is high.

A type of hypernatremia caused by excessive sodium intake through IV fluids, medications, or oral solutions.

A type of hypernatremia where the brain cells adapt to the high sodium concentration in the blood by increasing their own internal concentration of solutes, helping to maintain their volume.

A condition where the body's ability to retain water is impaired, often due to decreased production or response to antidiuretic hormone (ADH), leading to excessive water loss in urine.

A rare but serious neurological condition caused by rapid correction of chronic hyponatremia (low blood sodium levels). It damages nerve cells, especially in the pons, which is part of the brainstem.

A condition where the body retains too much water, leading to a dilution of sodium in the blood, resulting in hyponatremia.

The process of gradually raising the sodium concentration in the blood, typically done in patients with hyponatremia.

A dangerous complication of rapid sodium correction in patients with chronic hyponatremia. It can lead to severe neurological damage.

A goal of treatment for hyponatremia where the initial focus is on controlling severe symptoms by restoring the blood's tonicity (concentration) to a safe level.

A safe and gradual rise in serum sodium concentration, typically done after initial stabilization of severe hyponatremia.

The amount of sodium in the blood that should not be exceeded over a 24-hour period to minimize the risk of ODS. Avoid increasing serum sodium by more than 6-12 mEq/L in 24 hours.

The preferred treatment for hyponatremia, often given in a concentrated form to quickly raise sodium levels.

A type of diuretic used to increase the excretion of water, often administered with 3% NaCl to help raise sodium levels.

A medical approach that restricts water intake to help raise sodium levels in patients with hyponatremia.

A medication that helps block the effects of vasopressin, a hormone that promotes water retention, used in hyponatremia treatment.

The amount of sodium that needs to be added to the blood to reach a target concentration, calculated before administering sodium infusions.

A method for determining the effectiveness of a sodium infusion by comparing the sodium concentration of the infusate (solution) to the sodium and potassium levels excreted in the urine.