Fluid, Electrolyte, and Acid-Base Balance

A set of flashcards covering key vocabulary and concepts related to fluid, electrolyte, and acid-base balance.

Body Fluids

All the water and dissolved substances in the body; comprises approximately 50-60% of total body weight in adults.

Total Body Water (TBW)

The total amount of fluid in the body, typically 42 liters in a 70 kg adult male; represents approximately 60% of body weight in males and 50% in females.

Intracellular Fluid (ICF)

Fluid located inside cells; comprises approximately two-thirds (67%) of total body water or about 40% of body weight.

Extracellular Fluid (ECF)

Fluid located outside cells; comprises approximately one-third (33%) of total body water or about 20% of body weight.

Interstitial Fluid

Extracellular fluid surrounding and bathing tissue cells; comprises about 80% of extracellular fluid volume.

Plasma

The liquid portion of blood; comprises about 20% of extracellular fluid volume.

Transcellular Fluid

Specialized extracellular fluids separated from other fluids by epithelial membranes, including cerebrospinal fluid and digestive secretions.

Fluid Balance

The state where water intake equals water output, maintaining constant total body water.

Water Intake

Water entering the body through fluids, food, and metabolic processes, totaling approximately 2400-2500 mL/day.

Insensible Water Loss

Water loss that occurs without awareness, primarily through evaporation from the skin and respiratory tract.

Dehydration

A condition resulting from excessive water loss or inadequate intake, characterized by decreased body fluid volume.

Osmosis

The passive movement of water across a selectively permeable membrane from an area of lower solute concentration to one of higher concentration.

Osmotic Pressure

The pressure required to prevent osmosis, determined by the concentration of solutes that cannot cross the membrane.

Hypertonic Solution

A solution with higher osmotic pressure than body fluids, causing water to move out of cells.

Hydrostatic Pressure

The pressure exerted by a fluid against a wall or membrane; in capillaries, it forces fluid into interstitial space.

Starling Forces

Four pressures that determine fluid movement across capillary walls.

Osmoreceptors

Specialized neurons in the hypothalamus that monitor plasma osmolarity and trigger thirst and ADH release.

Antidiuretic Hormone (ADH)

A hormone that increases water reabsorption in kidneys by inserting aquaporins; released in response to increased osmolarity.

Electrolytes

Substances that dissociate into ions in water and can conduct electrical current; essential for nerve impulses and fluid balance.

Cation

A positively charged ion; major cations in body fluids include sodium, potassium, and calcium.

Acidosis

A physiological condition that tends to decrease blood pH, often due to excess hydrogen ions.

Acid-Base Buffer Systems

Chemical systems that resist changes in pH by binding or releasing hydrogen ions.

Respiratory Regulation of pH

Control of blood pH by adjusting breathing rate to eliminate or retain CO₂.

Arterial Blood Gas (ABG) Analysis

A test measuring pH, PCO₂, PO₂, and HCO₃⁻ in arterial blood to assess acid-base balance.