Fluid Balance
Which compartment contains most of the body's water?
The intracellular fluid (ICF)
Which hormone increases water reabsorption and thirst?
Antidiuretic hormone (ADH)
What condition results from water loss without electrolyte loss?
Dehydration -- hypernatremia
What is the normal blood pH range?
7.35 - 7.45
What are the normal ranges for plasma CO2 and HCO3?
CO2 = 35 - 45 mmHg
HCO3 = 22 - 26 mEq/L
What are the main cations in the ICF and ECF?
ICF - Potassium (K+)
ECF - Sodium (Na+)
What triggers the release of aldoesterone?
Low BP activates the renin-angiotensin-aldosterone system (RAAS).
What condition results from excess water gain without electrolyte gain?
pH < 7.35 indicates what?
Acidosis
Which buffer system is the slowest?
Protein buffer system
True or False: Where water goes, sodium follows.
False! Where sodium goes, water follows.
Which hormone decreases sodium and water reabsorption and reduces thirst?
Atrial natriuretic peptide (ANP)
Which hormone increases calcium levels in the blood?
Parathyroid hormone (PTH)
What is the most common acid-base disorder?
Respiratory acidosis
Which buffer system acts immediately inside red blood cells?
Hemoglobin buffer system
What happens to cell size during dehydration?
Cells shrink (water moves out of the ICF and into the ECF).
Where does aldosterone act in the nephron?
Distal convoluted tubule and collecting ducts
Which hormone decreases calcium levels by increasing excretion at the kidneys?
Calcitonin
Which condition can result from hyperventilation?
Respiratory alkalosis
How does the body respond to metabolic acidosis?
Increases respiratory rate and depth to decrease CO2 (respiratory compensation)
In overhydration, which direction does water move?
Water moves from the ECF to the ICF (cells swell and lyse).
Explain how ADH and aldosterone differ in their effects on urine concentration.
ADH increases water reabsorption only --> more concentrated urine
Aldosterone increases Na+ and water reabsorption and K+ secretion --> less concentrated
What is the role of calcitriol in phosphate regulation?
Increases phosphate reabsorption at the PCT.
What causes metabolic acidosis vs. metabolic alkalosis?
Acidosis: increase in metabolic acids (lactic acidosis, diarrhea)
Alkalosis: increase in bicarbonate (vomiting)
How do the kidneys compensate for respiratory acidosis?
Increase HCO3 absorption (decreases H+ concentration)