Mechanisms Involved in Maintenance of Fluid and Electrolyte Balance

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Defense of Tonicity[edit]

  • Defense of ECF tonicity is primarily the function of vasopressin-secreting and thirst mechanism
  • When the effective osmotic pressure of plasma rises, vasopressin secretion is increased and thirst is stimulated
  • When plasma becomes hypotonic, vasopressin secretion is decreased and solute-free water is excreted
  • In health, plasma osmolality ranges from 280-295mOsm/kg of H2O, with vasopressin maximally inhibited at 285mOsm/kg, and stimulated at higher values
  • Vasopressin increases the per