Fluids and Electrolytes Study Notes

Sodium (Na⁺)

Controls water balance, blood pressure, and nerve impulses. Found mainly in extracellular fluid.

Potassium (K⁺)

Essential for muscle contraction, especially heart rhythm. Found mainly in intracellular fluid.

Calcium (Ca²⁺)

Important for bone strength, muscle contraction, and blood clotting. Mostly found in extracellular fluid.

Magnesium (Mg²⁺)

Aids in nerve and muscle relaxation. Found mainly in intracellular fluid.

Chloride (Cl⁻)

Helps maintain fluid balance and works with sodium. Found mainly in extracellular fluid.

Phosphate (PO₄³⁻)

Key for energy production (ATP) and important for bones and teeth. Found mainly in intracellular fluid.

Bicarbonate (HCO₃⁻)

Maintains acid-base balance. Found primarily in extracellular fluid.

Osmosis

Movement of water from low solute concentration to high concentration.

Diffusion

Movement of solutes from high concentration to low concentration.

Isotonic solution

Same solute and water concentration as body fluids.

Hypotonic solution

Lower solute concentration than body fluids; can cause cell swelling.

Hypertonic solution

Higher solute concentration than body fluids; can cause cell shrinkage.

Dehydration

Loss of water, categorized as isotonic, hypertonic, or hypotonic.

Overhydration

Excess fluid in the body, categorized as isotonic, hypotonic, or hypertonic.

Thirst mechanism

Stimulated by increased ECF volume and decreased osmolality, prompting water intake.