Hole's Human Anatomy & Physiology - Chapter 21: Water, Electrolyte, and Acid-Base Balance

Vocabulary practice flashcards covering fluid compartments, water and electrolyte intake/output, hormone regulation, chemical/physiological buffer systems, and acid-base imbalances from Chapter 21.

Balance

A state of constancy in which equal quantities of water and electrolytes enter and leave the body to maintain homeostasis.

Intracellular fluid compartment

The fluid compartment located inside cells, which contains approximately $63\%$ of the body's total water volume.

Extracellular fluid compartment

The fluid compartment located outside cells, which contains approximately $37\%$ of total body water and comprises interstitial fluid, blood plasma, lymph, and transcellular fluid.

Transcellular fluid

A specialized portion of extracellular fluid separated by epithelial layers, including cerebrospinal fluid, aqueous and vitreous humors, synovial fluid, and serous fluid.

Interstitial fluid

Extracellular fluid occupying the microscopic spaces between tissue cells.

Water of metabolism

Water produced as a byproduct of oxidative nutrient metabolism, accounting for about $10\%$ ($250\,mL$) of daily fluid intake.

Sensible perspiration

Visible water loss through active sweating, accounting for about $6\%$ ($150\,mL$) of daily water output.

Insensible perspiration

Unnoticed water evaporation through the skin, which together with water lost from the lungs during breathing accounts for approximately $28\%$ ($700\,mL$) of daily output.

Osmoreceptor-ADH mechanism

A hypothalamic regulatory process where shrinking osmoreceptors trigger the release of antidiuretic hormone (ADH), stimulating renal distal convoluted tubules and collecting ducts to reabsorb water.

Dehydration

A condition in which water output exceeds intake, causing extracellular fluid to concentrate and drawing water out of cells via osmosis.

Water intoxication

A state caused by excessive water intake that dilutes body fluids, leading to hyponatremia and an imbalance between water and electrolytes.

Edema

An abnormal accumulation of extracellular fluid within the interstitial spaces.

Electrolyte balance

A physiological condition achieved when the quantities of electrolytes gained by the body equal those lost through excretion.

Aldosterone

An adrenal cortex hormone stimulated by elevated plasma potassium levels that promotes renal tubular reabsorption of sodium ions ($Na^+$) and secretion of potassium ions ($K^+$).

Parathyroid hormone (PTH)

A hormone released in response to decreased plasma calcium ($Ca^{+2}$) that increases osteoclast activity, promotes intestinal calcium absorption, and conserves renal calcium while excreting phosphate.

Hyponatremia

An abnormally low blood sodium ion concentration ($[Na^+]$), commonly caused by prolonged sweating, vomiting, or excessive water consumption.

Hypernatremia

An abnormally high blood sodium ion concentration ($[Na^+]$) caused by severe water loss, leading to central nervous system disturbances including confusion, stupor, and coma.

Hypokalemia

An abnormally low blood potassium ion concentration ($[K^+]$), which causes muscle weakness, paralysis, and cardiac conduction disturbances.

Hyperkalemia

An abnormally elevated blood potassium ion concentration ($[K^+]$), resulting from kidney disease or aldosterone deficiency, which can trigger skeletal muscle paralysis and cardiac arrest.

Chemical buffer systems

Rapid-acting combinations of chemicals in body fluids that convert strong acids into weak acids or strong bases into weak bases to resist sudden shifts in pH.

Bicarbonate buffer system

A chemical buffer system in which bicarbonate ions ($HCO_3^-$) convert strong acids to weak carbonic acid ($H_2CO_3$), and carbonic acid converts strong bases into weak bicarbonate.

Phosphate buffer system

A chemical buffer system important in intracellular and renal tubular fluids consisting of monohydrogen phosphate ($HPO_4^{-2}$) and dihydrogen phosphate ($H_2PO_4^-$).

Protein buffer system

A chemical buffer system utilizing amino acid functional groups, where the $-COO^-$ group accepts excess hydrogen ions and the $-NH_3^+$ group releases hydrogen ions in basic conditions.

Physiological buffers

Slower-acting secondary regulatory systems, specifically the respiratory mechanism ($CO_2$ excretion) and renal mechanism ($H^+$ excretion), that eliminate excess acids or bases.

Acidosis

A clinical state characterized by an arterial blood pH below $7.35$, caused by the accumulation of acids or loss of bases.

Alkalosis

A clinical state characterized by an arterial blood pH above $7.45$, caused by the loss of acids or accumulation of bases.

Respiratory acidosis

Acidosis resulting from an accumulation of carbon dioxide ($CO_2$) and carbonic acid ($H_2CO_3$) due to hypoventilation, airway obstruction, or reduced alveolar gas exchange.

Metabolic acidosis

Acidosis caused by the accumulation of nonrespiratory acids (e.g., ketones in diabetes or renal failure) or excessive loss of bases (e.g., prolonged diarrhea).

Respiratory alkalosis

Alkalosis resulting from hyperventilation, which drives an excessive loss of carbon dioxide ($CO_2$) and a decrease in carbonic acid ($H_2CO_3$).

Metabolic alkalosis

Alkalosis resulting from excessive loss of hydrogen ions (via gastric drainage or vomiting) or excessive intake of basic substances such as antacids.

Compensation

The physiological resistance to an abnormal pH shift by adjusting chemical buffering, respiratory carbon dioxide excretion, and renal hydrogen ion excretion.