BP106T • Unit 3Topic 1 of 3⏱ 5 Min Read

1. Physiological Roles of Major Body Electrolytes & Fluid Balance

💡 Core Concept & Clinical Context:

Electrolytes are inorganic minerals that dissociate into electrically charged ions ($Cations^+$ and $Anions^-$) in aqueous biological fluids. Total Body Water accounts for ~60% of adult body weight, partitioned into Intracellular Fluid (ICF, 2/3 of total water) and Extracellular Fluid (ECF, 1/3 of total water: interstitial fluid and blood plasma). The principal Extracellular Cation is Sodium ($Na^+$, 135-145 mEq/L) which maintains osmotic pressure and fluid volume, paired with Extracellular Anions Chloride ($Cl^-$, 98-106 mEq/L) and Bicarbonate ($HCO_3^-$, 22-28 mEq/L). The principal Intracellular Cation is Potassium ($K^+$, 140-150 mEq/L inside cells; 3.5-5.0 mEq/L in plasma) essential for resting membrane potentials and cardiac rhythmicity, paired with Intracellular Anions Phosphate ($HPO_4^{2-}$) and proteins.

Clinical Scenarios & Pharmacopoeial Examples:

1Clinical Consequences of Severe Electrolyte Imbalances

Pathophysiological emergencies resulting from electrolyte deviations.

Step-by-Step Breakdown:

•• Hyperkalemia (Plasma K+ > 5.5 mEq/L): Caused by renal failure or potassium-sparing diuretics; causes peaked T-waves on ECG, fatal ventricular fibrillation, or cardiac arrest.

•• Hypokalemia (Plasma K+ < 3.5 mEq/L): Caused by severe diarrhea, vomiting, or loop diuretics (Furosemide); causes U-waves on ECG, muscle weakness, paralytic ileus, and arrhythmias.

•• Hyponatremia (Plasma Na+ < 135 mEq/L): Causes cerebral cellular edema, seizures, coma.

•• Hypocalcemia (Plasma Ca2+ < 8.5 mg/dL): Causes neuromuscular irritability, Carpopedal spasm, Tetany (positive Trousseau and Chvostek signs).

Comparison & Reference Table:

Electrolyte Ion	Primary Location	Normal Plasma Range	Core Physiological Function
Sodium ($Na^+$)	Extracellular Fluid (ECF)	135 - 145 mEq/L	Primary determinant of ECF osmotic pressure, nerve action potentials
Potassium ($K^+$)	Intracellular Fluid (ICF)	3.5 - 5.0 mEq/L	Resting membrane potential, cardiac repolarization, neuromusculature
Calcium ($Ca^{2+}$)	Bone (99%) / ECF (1%)	8.5 - 10.5 mg/dL	Blood coagulation cascade, bone mineralization, muscle cross-bridge contraction
Magnesium ($Mg^{2+}$)	Intracellular / Bone	1.5 - 2.5 mEq/L	Essential cofactor for over 300 ATP-dependent metabolic enzymes
Chloride ($Cl^-$)	Extracellular Fluid	98 - 106 mEq/L	Maintains electroneutrality, gastric $HCl$ acid production
Bicarbonate ($HCO_3^-$)	Extracellular Fluid	22 - 28 mEq/L	Primary physiological blood buffer neutralizing metabolic acids

📋Key Takeaways & Exam Highlights

ECF Dominant Ions: $Na^+, Cl^-, HCO_3^-$ (Regulates arterial blood pressure and ECF volume).
ICF Dominant Ions: $K^+, Mg^{2+}, HPO_4^{2-}$ (Regulates cellular metabolism and intracellular enzyme systems).
Calcium Homeostasis: Maintained by Parathyroid Hormone (increases blood $Ca^{2+}$) and Calcitonin (decreases blood $Ca^{2+}$).

🇮🇳 हिन्दी व्याख्या (1. Physiological Roles of Major Body Electrolytes & Fluid Balance)

सोडियम (Na+) खून और कोशिकाओं के बाहर पानी का संतुलन रखता है। पोटैशियम (K+) कोशिकाओं के अंदर रहकर दिल की धड़कन को नियंत्रित करता है। पोटैशियम की कमी (Hypokalemia) या अधिकता (Hyperkalemia) से दिल का दौरा पड़ सकता है।