Chapter 8_1 flashcards
(26 cards)
Importance of pH Balance in the Body
Alterations in pH disrupt body functioning, especially protein structure and function. pH must be maintained in a narrow range (blood pH 7.35-7.45). [cite: 2]
Acid: Definition
Any compound that donates hydrogen ions (H+) in solution. [cite: 3]
Base: Definition
A compound that accepts H+ ions in solution. [cite: 3]
Acidic Solution vs. Basic (Alkaline) Solution
Acidic Solution: H+ ions predominate, lower pH value. [cite: 3, 5] Basic (Alkaline) Solution: Basic ions (e.g., OH-) predominate, higher pH value. [cite: 3, 5]
pH Scale: Concept
A scale from 0 to 14 where pH is the negative logarithm of H+ concentration. Lower pH = more acidic (higher H+), Higher pH = more basic/alkaline (lower H+). Neutral is pH 7. [cite: 3, 5]
Volatile Acid: Definition & Formation in Body
An acid that can be converted to a gas. In the body, CO2 combines with water to form carbonic acid (H2CO3), a volatile acid. Enzyme: carbonic anhydrase (in RBCs). H2CO3 dissociates into CO2 (exhaled by lungs) and water. [cite: 4]
Non-volatile (Fixed) Acids: Definition & Examples
Acids that are not converted to CO2 and thus not eliminated by the lungs. Examples: Ketones, lactic acid. [cite: 4]
Metabolic Acids (Examples)
CO2 (forms carbonic acid), Ketones (from fat metabolism), Lactic acid (from anaerobic metabolism). [cite: 5]
Metabolic Bases (Example)
Form from the metabolism of negatively charged amino acids. [cite: 5]
Buffer Systems: General Purpose
Help prevent large changes in pH by donating H+ ions when a solution is too basic, or absorbing H+ ions when a solution is too acidic. [cite: 2]
Three Major Buffer Systems in the Body
- Protein (largest system, e.g., hemoglobin). 2. Phosphate (regulates intracellular pH). 3. Carbonic acid-bicarbonate system (involves CO2, H2CO3, H+, HCO3-; used by lungs/kidneys). [cite: 6]
Carbonic Acid-Bicarbonate Buffer System: Chemical Equation
CO2 + H2O <=> H2CO3 <=> H+ + HCO3- (Carbon dioxide + Water <=> Carbonic acid <=> Hydrogen ion + Bicarbonate ion). [cite: 7]
Carbonic Acid-Bicarbonate System: Role of Carbonic Anhydrase
Enzyme present in erythrocytes (RBCs) that catalyzes the formation of carbonic acid (H2CO3) from CO2 and H2O. [cite: 7]
Carbonic Acid-Bicarbonate System: Equation Shift with Elevated CO2
When CO2 is elevated, the equation CO2 + H2O <=> H2CO3 <=> H+ + HCO3- moves toward the RIGHT, forming more H+ and HCO3-. [cite: 8]
Carbonic Acid-Bicarbonate System: Equation Shift with Elevated H+
When H+ ions are elevated, the equation CO2 + H2O <=> H2CO3 <=> H+ + HCO3- moves toward the LEFT, converting H+ ions (with HCO3-) to H2CO3, then to CO2 and water, so CO2 can be exhaled. [cite: 8]
Compensation (Acid-Base Balance): Definition
Process by which the lungs and kidneys attempt to adjust pH disturbances, primarily using the carbonic acid-bicarbonate buffering system. [cite: 9]
Lungs vs. Kidneys in Compensation: Speed and Duration
Lungs: Respond within minutes to acid-base disturbances; response cannot be maintained indefinitely. [cite: 9] Kidneys: Take hours to days to compensate; response can be maintained for longer. [cite: 9]
Arterial Blood Gases (ABGs): Purpose
Measure oxygenation, acidity, and alkalinity of arterial blood. Help determine presence and cause (respiratory or metabolic) of acid-base imbalances. [cite: 14]
Normal ABG Values
Blood pH: 7.35 - 7.45 [cite: 15]
PCO2: 35 - 45 mm Hg [cite: 15]
PO2: 90 - 100 mm Hg [cite: 15]
HCO3-: 22 - 26 mEq/L [cite: 15]
SaO2 (saturation of hemoglobin with oxygen): 95% - 100% [cite: 15]
Terminology from ABGs: Hypercapnia, Hypocapnia, Hypoxia/Hypoxemia
Hypercapnia: Elevated PCO2 (>45 mm Hg). [cite: 16] Hypocapnia: Decreased PCO2 (<35 mm Hg). [cite: 16] Hypoxia or Hypoxemia: Low PO2 (<90 mm Hg, though clinical significance varies). [cite: 16]
Acidosis (Acidemia): Definition (pH)
Blood pH less than 7.35. [cite: 17]
Alkalosis (Alkalemia): Definition (pH)
Blood pH greater than 7.45. [cite: 17]
Origin of Acid-Base Disturbance: Respiratory vs. Metabolic
Respiratory: Abnormality in carbon dioxide (CO2) levels. pH and PCO2 levels move in OPPOSITE directions. [cite: 17]
Metabolic: Cause not related to pulmonary system/CO2. pH and PCO2 levels move in the SAME direction (or PCO2 is normal initially). [cite: 17]
Anion Gap (AG): Definition & Calculation
Represents the concentration of unmeasured anions in the bloodstream. Calculated as: (Measured Cations [Na+ + K+]) - (Measured Anions [Cl- + HCO3-]). [cite: 20]
