Fluid, Electrolytes, and Acid/Base Balance

Which electrolyte is most abundant in extracellular fluid (ECF)?

Sodium (Na⁺).

Which electrolyte is most abundant in intracellular fluid (ICF)?

Potassium (K⁺).

What happens to a cell in a hypotonic solution?

Water enters the cell → the cell swells and may burst.

What happens to a cell in a hypertonic solution?

Water leaves the cell → the cell shrinks (crenates).

What is the main buffer system in the blood?

The bicarbonate buffer system:
CO₂ + H₂O ⇌ H₂CO₃ ⇌ H⁺ + HCO₃⁻

What organ system is the fastest to compensate for pH imbalances?

The respiratory system (acts within minutes by changing CO₂ levels).

What organ provides long-term pH regulation?

The kidneys, by excreting H⁺ and reabsorbing HCO₃⁻.

What condition results from excess CO₂ in the blood?

Respiratory acidosis.

What condition results from excess loss of CO₂ (like hyperventilation)?

Respiratory alkalosis.

How do the kidneys respond to acidosis?

Excrete more H⁺ and retain more HCO₃⁻.

What is osmosis?

The movement of water across a semipermeable membrane from low solute to high solute concentration.

What causes water to move between fluid compartments?

Osmotic pressure and hydrostatic pressure.