Fluid, Electrolyte, and Acid-Base Homeostasis

Vocabulary flashcards covering fluid compartments, balance, electrolytes, and acid-base concepts.

Intracellular Fluid

All fluid contained inside cells; 2/3 of all body fluids.

Extracellular Fluid

All fluid outside cells; 1/3 of all body fluids.

Interstitial Fluid

Fluid between the cells of the body; most extracellular fluid (¾).

Intravascular Fluid Space

Mostly blood plasma but also lymph, CSF, synovial fluid, aqueous humor, endolymph and perilymph, pleural fluid, and pericardial fluid.

Edema

Excess interstitial fluid collects, causing swelling in the tissues.

Causes of Edema

Increased blood pressure, increased capillary permeability, decreased concentration of plasma proteins, obstruction in lymphatic drainage.

Normal Fluid Intake

Ingestion (2300mL/day) and metabolic synthesis of water (200mL/day).

Normal Fluid Loss

The kidneys (1500mL/day), evaporation from the skin (600mL/day), respiratory tract (300mL/day), and in the feces (100mL/day).

Antidiuretic Hormone (ADH) / Vasopressin

Directly regulates water loss in the kidneys by increasing permeability of the collecting ducts to water, producing a concentrated urine.

Hormones Regulating Renal Na+ and Cl– Reabsorption/Excretion

Angiotensin II and aldosterone promote urinary Na+ and Cl– reabsorption (and water by osmosis); Atrial natriuretic peptide (ANP) promotes excretion of Na+ and Cl– followed by water excretion to decrease blood volume.

Ions

Form when electrolytes dissolve and dissociate; can be positively charged (cations) or negatively charged (anions).

Cations

Positively charged ions.

Anions

Negatively charged ions.

Functions of Electrolytes

Control osmosis of water between body fluid compartments, help maintain the acid-base balance, carry electrical current, and serve as cofactors.

Buffer Systems

Acts quickly to temporarily bind excess H+ or OH -, sequestering the highly reactive ions until they can be permanently excreted.

Respiratory Acidosis

CO2 accumulates because of hypoventilation.

Metabolic Acidosis

Non-respiratory acids accumulate, as seen in diabetic ketoacidosis or aspirin overdose.

Respiratory Alkalosis

Too much CO2 is lost because of hyperventilation.

Metabolic Alkalosis

Non-respiratory acids are lost.