Acid Base Balance
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58 Terms
normal arterial blood pH
7.35-7.54
what does pH measure?
the concentration of hydrogen ions (H+) in a solution
what happens to pH when H+ increases?
pH decreases (more acidic)
what happens to pH when H+ decreases?
pH increases (more alkaline)
acid
a substance that donates H+ ions
base
a substance that accepts H+ ions
acidemia
increased H+ in the blood (low blood pH)
acidosis
a process that increased H+ in body fluids
alkalemia
decreased H+ in the blood (high blood pH)
alkalosis
a process that causes decreased H+ in body fluids
pH range
0-14
what is the pH of pure water?
7 (neutral)
is the pH scale logarithmic or linear?
logarithmic
how much more acidic is pH 5 compared to pH 6?
10 time more acidic
what is the relationship between H+ and pH?
they are inversely related
normal urine pH
4.8-7.5
normal gastric juice pH
1-5
what equation describes blood pH?
Henderson-Hasselbalch equation
what is the Henderson-Hasselbalch equation?
pH = 6.1 + log(HCO3/H2CO3)
how is carbonic acid (H2CO3) calculated?
H2CO3 = 0.03 * PaCO2
normal bicarb (HCO3)
24 mEq/L
normal PaCO2
40 mmHg
normal calculated carbonic acid
1.2 mEq/L
what pH results from HCO3 = 24 and PaCO2 = 40?
7.40
what are the 3 pH regulation systems?
1. chemical buffers
2. respiratory system
3. renal system
which system responds first?
chemical buffers
which system responds in 1-3 mins?
respiratory system
which system takes 24-48 hours?
renal system
which system provides the most powerful long-term control?
kidneys
what is the primary chemical buffer?
carbonic acid-bicarbonate buffer
what % of buffering is from the carbonic acid-bicarbonate system?
53%
what % is protein buffering?
42%
what % is phosphate buffering?
5%
which proteins act as buffers?
albumin and hemoglobin
what is the carbonic acid reaction?
CO₂ + H₂O ⇌ H₂CO₃ ⇌ H⁺ + HCO₃⁻
what does the respiratory system regulate?
CO2
hyperventilation causes what change in CO2?
decreases CO2
hyperventilation causes what change in pH?
increases pH (alkalosis)
why does hyperventilation increase pH?
less CO2 means less H+ is produced
hypoventilation causes what change in CO2?
increases CO2
hypoventilation causes what change in pH?
decreases pH (acidosis)
why does hypoventilation decreases pH?
more CO2 produces more H+
does CO2 cross the blood-brain barrier?
yes
does H+ cross the blood-brain barrier?
no
does bicarb cross the blood-brain barrier?
no
what stimulates ventilation in the brain?
increased H+ in the cerebrospinal fluid
how much of an increase in PaCO2 can stimulate ventilation?
about 2-3 mmHg
during acidosis, what do the kidneys excrete?
H+
during acidosis, what do the kidneys retain?
HCO3-
during alkalosis, what do the kidneys execrete?
HCO3-
during alkalosis, what do the kidneys retain?
H+
which organs can eliminate H+ directly?
kidneys
what are fixed (nonvolatile) acids?
acids that cannot be eliminated by the lungs
examples of fixed acids
lactic acid & ketoacids
which organ eliminates fixed acids?
kidneys
what is the body's major volatile acid?
CO2
which organ eliminates volatile acid?
lungs
approximately how much CO2 does a normal adult produce each day?
about 300 L