Differentiate normal body water and electrolyte composition and movement in the fluid compartments.
Explain the regulation of water balance within the body.
Explain the roles and regulation of electrolytes and electrolyte balance within the body. USLO 10.4 Explain the regulation of Acid-Base balance within the body.
Differentiate four homeostatic imbalances of fluid and electrolytes and explain what is occurring from a physiological perspective.
Sample Solution
Normal Body Water and Electrolyte Composition and Movement in Fluid Compartments
The human body is remarkably composed of water, accounting for approximately 50-60% of total body weight in adults, though this percentage varies with age, sex, and body fat. This water is not static but is distributed among various fluid compartments, each with a distinct electrolyte composition.
Fluid Compartments:
Intracellular Fluid (ICF):
- Location: Fluid found inside the cells. It constitutes about two-thirds (60-65%) of the total body water.
- Composition: The primary cation in the ICF is Potassium (K+), and the primary anions are Phosphate (PO43−) and proteins. Sodium (Na+) and Chloride (Cl−) concentrations are very low.
- Movement: Water moves into and out of the ICF primarily through osmosis, driven by changes in osmotic pressure gradients across the cell membrane. The sodium-potassium pump (Na+/K+ATPase) actively maintains the high intracellular K+ and low Na+ concentrations, which are crucial for cell volume and electrical potential.
Extracellular Fluid (ECF):
- Location: Fluid found outside the cells. It constitutes about one-third (35-40%) of the total body water. The ECF is further divided into:
- Interstitial Fluid (ISF): The fluid that bathes the cells, found in the spaces between cells and outside of blood vessels. It makes up about 75% of the ECF.
- Intravascular Fluid (Plasma): The fluid component of blood, found within blood vessels. It makes up about 20-25% of the ECF.