Fluid Balance and Osmolarity Review

What must be closely regulated to help maintain blood pressure?

What is necessary to prevent the swelling or shrinking of cells?

Which of the following contributes to water input in the body?

Which type of loss is considered insensible?

What must occur to maintain stable water balance in the body?

What effect does increased osmolarity have on water concentration?

Which ion is primarily responsible for extracellular fluid (ECF) osmolarity?

What does ICF stand for and which ion is significant in it?

How does increased osmolarity affect solute concentration?

In which fluid is sodium the primary solute?

What does the equality of total concentration of Na+ and other solutes in ECF to K+ and other solutes inside the cell indicate?

Why is it important for Na+ and K+ concentrations to be balanced across the cellular membranes?

Which of the following best describes the relationship between Na+ and K+ in terms of cellular equilibrium?

What implication does the equal total concentration of solutes have on cellular functions?

What occurs when there is a disturbance in the balance of Na+ and K+ concentrations?

Fluid Balance

Two factors regulate fluid balance: ECF volume and ECF osmolarity.
ECF volume regulation is vital for maintaining blood pressure.
Long-term ECF volume regulation requires maintaining salt balance.
ECF osmolarity regulation prevents cell swelling or shrinking.
Water balance controls ECF osmolarity.

Water Input and Output

Water input comes from drinking fluids, eating solid foods, and metabolically produced water (oxidation of carbohydrates, lipids, and proteins).
Water output includes insensible loss (lungs, non-sweating skin), sensible loss (sweating, feces, urine), and excretion.

ECF Osmolarity

Increased ECF osmolarity means a higher solute concentration and lower water concentration.
Sodium (Na+) is the primary solute in ECF, determining ECF osmolarity.
Potassium (K+) is the main solute responsible for ICF osmolarity.
ECF and ICF solute concentrations are equal.
Severe hypertonicity (hyperosmolarity) of ECF can affect brain cells and function, leading to mental confusion.

Body Fluid Compartments

Blood vessel walls separate plasma and interstitial fluid.
Cellular plasma membranes separate ECF and ICF.

Factors Affecting Total Body Water

Age, lean tissue, and gender influence body water content.
Lean tissue has a higher fluid content than fat tissue.
Males have more lean tissue, resulting in more body fluids.
Body fluid decreases with age due to loss of lean tissue.

Differences Between ECF and ICF in 70 kg Adult Male

Feature	ECF	ICF
Volume	15L	25L
Na+	142 mmol/L	10 mmol/L
K+	4 mmol/L	140 mmol/L
Ca++	2.5 mmol/L	Negligible
Cl-	105 mmol/L	4 mmol/L
HCO3-	25 mmol/L	10 mmol/L
Protein-	17 mEq/L	65 mEq/L
pH	7.4	7.2
Osmolarity	280-300 mOsmol/L	280-300 mOsmol/L

Important Differences Between ECF & ICF

Feature	ICF	ECF
Na+	Low	High
K+	High	Low
Ca++	Negligible	High
Cl-	Low	High
Protein-	High	Low
Osmolarity	Equal to ECF	Equal to ICF

This quiz covers the essential concepts of fluid balance, including the regulation of ECF volume and osmolarity. You'll explore how these factors maintain blood pressure and influence water input and output. Test your knowledge about the roles of sodium and potassium in osmolarity and their effects on cellular health.