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ACID-BASE BALANCE. pH is a measure of H + pH = - log [H + ] Importance: Chemical reactions. Acid + Base = Salt Water (NEUTRALIZATION REACTION: HCl + NaOH NaCl + H 2 O ). pH SCALE. Logarithmic 1.0 to 14.0 7.0 = neutral (chemical) 7.4 = normal (biological)
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pH SCALE
• Logarithmic• 1.0 to 14.0• 7.0 = neutral (chemical)• 7.4 = normal (biological)• <7.0 (7.4) = acidic• >7.0 (7.4) = alkaline (basic)• body pH range = 7.35 to 7.45
ACIDS AND BASES
• Acid = releases H+ = proton donor
• Base = accepts H+ = proton acceptor
• Strong acid vs. weak acid
• Strong base vs. weak base
BUFFER SYSTEMS• Buffer = substance preventing extreme
fluctuations of pH• Strong acids/bases to weak ones• Work in buffer pairs; a base and an acid• Action:– BB + strong acid weak acid + salt– BA + strong base weak base + water
• Systems: bicarbonate; phosphate; protein
BICARBONATE BUFFERS
• Important in blood• Buffer pair = NaHCO3/H2CO3
• HCl + NaHCO3 H2CO3 + NaCl
• NaOH + H2CO3 NaHCO3 + H2O
PHOSPHATE BUFFERS
• Important in kidney• Buffer pair = Na2HPO4/NaH2PO4
• HCl + Na2HPO4 NaH2PO4 + NaCl
• NaOH + NaH2PO4 Na2HPO4 + H2O
PROTEIN BUFFERS• Important in cells• Amphoteric• Side groups:– COOH acts as acid – donates H+
– NH2 acts as base – accepts H +
• Hb can act as a buffer
Respiratory Control of pH• Review respiratory centers of brain • Review respiratory equation• Review chemoreceptors• It is fast acting when buffers need help• Control lasts relatively short time• NOT a long term solution• H+ = pH = resp. equation left = ventilation• Consider the opposite scenario
Renal Control of pH• Kidney slow to respond to pH changes• Responds only after persistent changes• Compensates for a relatively long period• NOT a solution to chronic pH problems• Rids the body of H+ by tubular secretion– PCT, DCT, CD
• Also:– Reabsorption of HCO3
-
– Regulation of PO4 -3
– Production and elimination of NH3
Summary of Kidney Action
Blood Tubule Cells Filtrate CO2 CO2+ H2O
H2CO3-
HCO3- + H + H + + Na2HPO4
Na+ + NaH2PO4Na+Na+
HCO3-
+
NH3 H+NH3 +
NH4+
(for excess H+)
Acidosis & Alkalosis
• Look at the listed values in the above order
Range Acidosis Alkalosis
pH 7.35-7.45 < 7.4 > 7.4
pCO235-45 mmHg > 45 mmHg < 35 mmHg
HCO3- 22-28 mEq/L < 22 mEq/L > 28 mEq/L
Acidosis & AlkalosisAcidosis Alkalosis
Respiratory •Respiratory problems
•Rapid, shallow breathing
•Overdose
•Brain stem injury
•Hyperventilation
•Brain stem injury
Metabolic •Diarrhea
•Renal disease
•Starvation
•Excess alcohol
•Increased ECF
•Vomiting
•Excess diuretics
•Excess bicarbonate
•Constipation
•Excess aldosterone
Compensation
• One system helping another to alleviate an acid/base problem:– An overload of the buffer system results in an
increase in breathing rate; the respiratory system is compensating.
Fluids & Electrolytes• Body water content
• Fluid compartments:– Intracellular– Extracellular• Plasma• Interstitial fluid
Fluid Composition
p. 1043
1. Note sodium and potassium
2. Note similarity of plasma & interstitial fluid except for protein
Fluid Movement
• Water follows osmotic and hydrostatic pressure gradients
Intracellular Interstitial Plasma
Disorders of Water Balance
• Dehydration– Water loss exceeds intake; When?– Diabetes– Decreased volume = hypovolemic shock– Water movement out of cells
• Hypotonic hydration (Water intoxication)– Excess water– Diluted ECF– hyponatremia
• Edema
Respiratory Centers
• Medulla• Pons– Apneustic – works to smooth transition between
inspiration and expiration– Pneumotaxic (pontine respiratory group) • Inhibits respiratory center• fine tunes rhythm• Prevents overinflation