Key Concepts of Body Fluids and Electrolytes

Total Body Mass

• Total body mass consists of solids and fluids.
  • Female: approximately 45% solids
  • Male: approximately 40% solids
• Fluid composition:
  • Females: about 55% fluids
  • Males: around 50% fluids
  • Hypothesis for differences: Fat composition vs. muscle composition.

Breakdown of Body Fluids

• Total body fluid is about 55% to 60% and includes water and dissolved solutes.
• Breakdown of body fluids:
  • Intracellular Fluid (ICF):
  • Comprises 2/3 of total body fluid.
  • Found within cells.
  • Extracellular Fluid (ECF):
  • Comprises 1/3 of total body fluid.
  • Further divided into:
    • Interstitial Fluid: 80% of ECF, fluid between cells.
    • Blood Plasma: 20% of ECF, fluid component of blood.

Water Gain and Loss

• Water gain is equal to water loss, approximately 2500 mL.
  • Sources of water gain:
  • Ingested liquids (water, coffee, soda).
  • Ingested foods (water content varies).
  • Metabolic water from cellular respiration.
• Water loss occurs via:
  • Kidneys: largest contributor via urine.
  • Skin: through sweat.
  • Lungs: water loss during exhalation.
  • GI Tract: minimal loss, primarily during defecation.

Electrolyte Imbalances

• Electrolytes are vital for maintaining fluid balance and homeostasis. Significant imbalances can disrupt bodily functions.

Sodium (Na)

• Functions:
  • Muscle contraction
  • Nerve conduction
• Imbalances:
  • Hyponatremia (low sodium):
  • Symptoms include mental confusion, muscle weakness, and headaches.
  • Hypernatremia (high sodium):
  • Symptoms may include intense thirst and hypertension.

Chloride (Cl)

• Important as sodium chloride (NaCl), especially lost in sweat.
• Imbalances lead to similar issues as sodium due to their relationship.

Potassium (K)

• Involved in muscle contraction and regulating fluid volume.
• Imbalances:
  • Hypokalemia (low potassium):
  • Symptoms include muscle fatigue and confusion.
  • Hyperkalemia (high potassium):
  • Symptoms can result in nausea and may lead to death through heart complications.

Calcium (Ca)

• Key for nerve excitability, muscle response, and blood coagulation.
• Imbalances:
  • Hypocalcemia (low calcium):
  • Symptoms include numbness, tetany, and convulsions.
  • Hypercalcemia (high calcium):
  • Symptoms can include lethargy and may lead to coma.

Additional Notes

• Importance of electrolyte replenishment during physical activity; beverages like Gatorade help restore lost electrolytes and prevent conditions like hyponatremia.
• Discussion on thirst center in brain related to maintaining fluid balance and body hydration.