Chapter 30: Acid-Base Regulation Flashcards
Single free proton released from a hydrogen atom
Hydrogen ion
Compared with other ions, H concentration of the body fluids is normally kept at a low level. Normal H concentration
0.00004 mEq/L or 40 nEq/L
Molecules containing Hydrogen atoms that can release H ions in solutions
Acids
Molecules that can accept H ions
Base
How do proteins in the body function as bases?
Some amino acids have net negative charges that readily accept H
Excess removal of H from the body fluids
Alkalosis
Excess addition of H
Acidosis
One that rapidly dissociates and releases especially large amounts of H in solution
Strong acids
One that reacts rapidly and strongly with H
Strong bases
Normal variations of H concentration
3-5 nEq/L
Under extreme conditions, H concentration may vary from as low _____ and as high as _____
10 nEq/L and 160 nEq/L
Normal pH of arterial blood
7.4
Interstitial fluid has a pH of 7.35 similar to this body fluid due to extra amounts of CO2 released from the tissues to form H2CO3
Venous blood
Lower and upper limit of pH at which a person can live more than a few hours
6.8 - 8.0
pH of ICF
6.0-7.4
pH of urine
4.5-8.0
pH of gastric HCl
0.8
Hypoxia and poor blood to the tissues causes acid accumulation and decreased INTRAcellular pH. True or False
True
System that acts immediately (within seconds) to changes in H concentration
Buffer system
Any substance that can REVERSIBLY bind H
Buffer
What consists the bicarbonate buffer system?
Carbonic acid Bicarbonate salt (sodium bicarb)
Where Carbonic anhydrase is found
Walls of lung alveoli
Epithelial cells of renal tubules
CO2 dissolved in the blood is directly proportional to the amount of undissociated H2CO3. True or False
True
Allows one to calculate the pH of a solution if the molar concentration of HCO3 and PCO2 are known
Henderson-Hasselbalch equation
Shows the changes in pH of the ECF when the ratio of HCO3 to CO2 in ECF is altered
Bicarbonate buffer system titration curve
pK of the bicarbonate buffer system
6.1
The buffer system is most effective in the central part of the curve, where the pH is far from the pK of the system. True or False
False. pH is NEAR the pK of the system
Most powerful extracellular buffer in the body
BBS
Plays a major role in buffering renal tubular fluid and intracellular fluids
Phosphate Buffer System
Main elements of the phosphate buffer system
H2PO4 and HPO4
pK of the phosphate buffer system which allows the system to operate near its maximum buffering power
6.8
Among the plentiful buffers in the body because of their high concentrations especially in the cells
Proteins
What causes the pH in the ICF to change when there are changes in the ECF pH?
Diffusion of the elements of the BBS
60-70% of the total chemical buffering of the body fluids occurs where?
Inside the cells
H and HCO3 move through the cell membrane of cells slowly except which cell?
RBC
Buffering power of proteins is due to
- high concentration inside the cells
- pKs are fairly close to intracellular pH
All buffers in a common solution are in equilibrium with the same H concentration. Thus, any condition that changes the balance of one buffer system also changes the balance of all the others because the buffer systems buffer one another by shifting H back and forth between them
Isohydric principle
Effect of increased alveolar ventilation on PCO
Low PCO2
Increasing alveolar ventilation to about twice normal raises pH of ECF by about _____
0.23
Decrease in alveolar ventilation to 1/4 normal reduces the pH by ____
0.45
Increased H concentration increases alveolar ventilation. True or False
True
Change in ventilation rate per unit change is much greater at reduced levels of pH compared with increased levels of pH. True or False
True
Feedback gain of respiratory mechanism for controlling H concentration
1-3
Acid-base imbalance associated with impairment of lung function
Respiratory acidosis
Nonvolatile acids are acids which cannot be excreted by the lungs. The body produces about ______ each day
80 mEq
Primary mechanism for removal of nonvolatile acids by the body.
Renal excretion
Both HCO3 reabsorption and H excretion is accomplished through what process?
H secretion by the tubules
3 mechanisms to regulate ECF H concentration by the kidneys
H secretion
Filtered HCO3 reabsorption
Production of new HCO3
Tubular segment that does not participate in H secretion and HCO3 reabsorption
Thin descending and ascending limbs of the loop of Henle
80-90% of H secretion and HCO3 reabsorption occurs where
Proximal tubule
H secretion by a secondary active transport through the Na-H exchanger occurs in which parts of the tubule
Proximal tubule
Thick ascending limb of the loop of Henle
Early distal tubule
Energy for H secretion against a concentration gradient is derived from Na gradient favoring Na movement into the cell established by which transporter?
Na-K ATPase pump in the basolateral membrane
Secretory process of H begins when?
Diffusion of CO2 in the tubular cells or formed by metabolism in the tubular epithelial cells
How is filtered HCO3 reabsorbed?
- Combines with the secreted H to form H2CO3
- Dissociation into CO2 + H2O
- CO2 diffusion into the tubular cell
- Formation of H2CO3 catalyzed by Carbonic anhydrase
- Dissociation into HCO3 and H
- H secretion and HCO3 reabsorption
Method of HCO3 transport in the basolateral membrane of: A. Proximal tubules B. Late segments of the proximal tubule C. Thick ascending loop of Henle D. Collecting tubules and ducts
A. Na-HCO3 co-transport
B-D. Cl-HCO3 exchange
Excess H rids the body of nonvolatile acids produced by metabolism mostly through urinary excretion of free H. True or False
False. Mostly throguh combination with other urinary buffers
Mechanism of H secretion in the late distal tubules and continuing through the remainder of the tubular system
Primary active transport (H-ATPase)
For each liter of urine formed, a maximum of only _____ free H can be excreted.
0.03 mEq
4 urinary buffers
Phosphate
Ammonia
Citrate
Urate
2 effects of excess H
- reabsorption of all filtered HCO3
- production of new HCO3
Excreted product of the phosphate buffer system
Sodium salt (NaH2PO4)
Metabolism of glutamine ultimately results to production of what
2 NH4 ions
2 HCO3
Ammonia buffer system resulting to NH4 excretion and generation of new HCO3 through the dissociation of H2CO3 and combination of diffused NH3 and secreted H to form NH4 occurs in which tubular segment?
Collecting tubules
Effect of Chronic acidosis on NH4 excretion
Increased excretion of NH4
Normal values for pH, pCO2, HCO3
7.4
40 mmHg
24 mEq/L
