Acid/Base Flashcards
normal pH of the body
7.38-7.42; slightly alkaline
pH values of gastric secretion
1.0-3.5
pH values of urine
4.5-8.0
alkalosis
- high pH/low H+
- hyperexcitability in sensory neurons and muscles
- sustained respiratory muscle contraction
acidosis
very low pH/excess H+
-CNS depression, confusion, coma
Largest source of acid on a daily basis is..
CO2 from aerobic metabolism
pH homeostasis depends on what 3 mechanisms?
- buffers (first line of defence)
- ventilation (75% of disturbances)
- renal regulation of H+ and HCO3- (slowest)
buffer systems include..
proteins, phosphate ions, and HCO3-
intracellular buffers
cellular proteins (hemoglobin), phosphate ions
the most important extracellular buffer system
HCO3-
Plasma HCO3- conc. is approx. _______x conc. as plasma H+
600 000
What senses changes in plasma PCO2 and/or H+?
peripheral and central chemoreceptors; which signal to respiratory control center to adjust ventilation
Alterations in ventilation can..
correct disturbances in acid/base balance as well as cause them
How does the kidney handle the remaining 25% of pH disturbances?
- directly, by altering the rates of excretion or reabsorption of H+
- indirectly by changing the rate at which HCO3- buffer is reabsorbed or excreted
kidney uses what kind of buffers
ammonia and phosphate buffers
proximal tubule
secreted H+ and reabsorbs HCO3-
distal nephron
controls acid excretion
initial portion of the collecting duct
plays a significant role in fine regulation of acid-base balance
Type A intercalated cells
function in acidosis to increase H+ secretion and HCO3- and K+ are reabsorbed; hyperkalemia
Type B intercalated cells
function in alkalosis to increase H+ reabsorption and HCO3- and K+ secretion; hypokalemia
acid-base disturbances may be
respiratory or metabolic
respiratory induced changes in pH must be resolved via..
renal mechanism
respiratory acidosis
when alveolar hypoventilation results in CO2 retention and elevated plasma CO2
respiratory alkalosis
less common; occurs as a result of hyperventilation in absence of increased metabolic CO2 production
respiratory acidosis compensation by..
H+ excretion, HCO3- reabsorption
respiratory alkalosis compensation by…
HCO3- excretion and H+ reabsorption
metabolic acidosis
when dietary or metabolic input of H+ exceeds H+ excretion
ketoacidosis
results from excessive breakdown of fats and some amino acids
metabolic alkalosis common causes
- excessive committing of acidic stomach contents
- excessive ingestion of bicarbonate-containing antacids
renal response to metabolic alkalosis
HCO3- excreted and H+ reabsorbed
