Electrolyte Imbalance and Hormonal Regulation

Molecular Movement

• Molecules naturally move down the concentration gradient.
• Equilibrium is achieved when solute concentrations are equal on both sides.
• Diffusion requires no energy and occurs through a permeable membrane.

Types of Transport

• Facilitated Diffusion: Requires a carrier molecule for transport; e.g., glucose needs insulin for entry into cells.
• Active Transport: Movement against the concentration gradient, necessitating energy (ATP) produced in mitochondria; e.g., sodium-potassium pump.

Osmosis

• Primary method for water movement across cell membranes.
• Water moves from areas of higher concentration to lower concentration across a selectively permeable membrane.
• Movement ceases when concentrations equalize or when hydrostatic pressure exceeds osmotic pressure.

Pressure Concepts

• Osmotic Pressure: The pressure required to halt water movement due to osmosis.
• Hydrostatic Pressure: Pressure exerted by a fluid in a compartment; e.g., blood pressure.
• Proteins exert osmotic pressure by attracting water into their compartment (colloid osmotic pressure).

Osmolality vs. Osmolarity

• Osmolality: Measurement of solute concentration per weight of the solvent (kg of body water).
• Osmolarity: Measurement of solute concentration per volume of solution (liters).

Fluid Movement

• Isotonic: Equal solute concentration; minimal fluid movement.
• Hypotonic: Surrounding fluid is less concentrated; fluid moves into the cell, potentially causing rupture.
• Hypertonic: Surrounding fluid is more concentrated; fluid moves out, leading to cell shrinkage.

Fluid and Electrolyte Regulation

• Osmosis regulates fluid movement between intracellular and extracellular compartments.
• Key determinants include potassium (K+) and sodium (Na+) levels.
• Imbalances lead to shifts in fluid and can cause cellular dehydration or damage.

Hydration Status and Weight Changes

• Weight changes indicate fluid gain or loss; e.g., 1 liter of water equals 2.2 lbs or 1 kg.
• Sudden weight loss (e.g., from diuretics) can signify fluid loss.

Types of Dehydration

• Isosmotic: proportional loss of electrolytes and water; e.g., from bleeding or burns.
• Hyperosmotic: elevated extracellular osmolality; caused by conditions like diabetes insipidus or excessive sodium intake.
• Hypo-osmotic: sodium loss leads to water retention; commonly observed in adrenal insufficiency.

Hyponatremia

• Defined as serum sodium < 135 mEq/L; can arise from sodium loss, inadequate intake, or dilution.
• Classifications: hypovolemic (greater sodium loss than water), euvolemic (sodium loss without major water loss), hypervolemic (fluid overload scenario).

pH and Electrolyte Influence

• Acidosis leads to H+ ions moving into cells, causing hyperkalemia (increased potassium levels).
• Alkalosis causes H+ ions to move out, leading to hypokalemia (decreased potassium levels).

Calcium Functions and Regulation

• Critical for bone structure, blood clotting, hormone secretion, muscle contraction, and nerve impulse transmission.
• Regulated by:
  • Parathyroid Hormone: Raises extracellular calcium by promoting absorption.
  • Calcitonin: Lowers extracellular calcium by promoting deposition in bones.

Hypocalcemia

• Defined as serum calcium < 8.5 mg/dL; causes include hypoparathyroidism, vitamin D deficiency, and multiple blood transfusions.
• Symptoms: anxiety, irritability, tetany, and numbness. Signs include Trousseau's and Chvostek's responses.

This quiz explores the effects of aldosterone on electrolyte balance in the kidneys, particularly focusing on sodium, water retention, and potassium excretion. It also examines the concepts of acidosis and alkalosis, how the body compensates for these conditions, and the implications of diabetes ketoacidosis (DKA).