Integrative Physiology III Flashcards
[H+] is very tightly regulated: (4)
- enzymes
- blood clotting
- muscle contraction
- channels
Extreme range
compatible with life
(for a short time):
~ pH
6.8 to 8.0
fluid: Arterial Blood (ECF)
[H+]:
pH:
- 0x10-5
7. 4
fluid: Venous Blood (ECF)
[H+]:
pH:
- 5x10-5
7. 35
fluid: Interstitial Fluid (ECF)
[H+]:
pH:
- 5x10-5
7. 35
fluid: ICF
[H+]:
pH:
1x10-3 - 4x10-5
6.0-7.4
fluid: Urine
[H+]:
pH:
3 x10-2 – 1 x 10-5
4.5-8.0
fluid: Gastric Juice
[H+]:
pH:
160
0.8
sources of hydrogen ion gain (4)
generation of H from CO2
production of nonvolatile acids from the metabolism of proteins and other organic molecules
gain of H due to loss of HCO3- in diarrhea or other nongastric GI fluids
gain of H due to loss of HCO3- in the urine
sources of hydrogen ion loss (4)
utilization of H in the metabolism of various organic anions
loss of H in vomit
loss of H in urine
hyperventilation
Metabolic CO2 production
— mmol/day
20,000
Net gain of — mEq H+ daily.
40 – 80
Normal ECF [H+] =
0.00004 mEq/L.
Fixed” (Non-Volatile) Acid
Production: All Excreted by Kidneys
Adds ≈ — mEq/day
80
Protein Catabolism – (2)
sulfuric acid and HCl
Phospholipid Catabolism – (1)
phosphoric acid
Exercise, hypoxia –
lactic acid
Post-absorptive state, diabetes mellitus – (2)
acetoacetic, β-hydroxy-butyric acids
Nucleoprotein metabolism – (1)
uric acid
Three Primary Systems Regulate the [H+] in Body Fluids
1. Chemical (3)
Acid-base buffer systems (body fluids)
“instantaneous”
Does not add or remove H+ but keeps it “tied up” until balance can
be re-established
Three Primary Systems Regulate the [H+] in Body Fluids
2. Respiratory system (3)
Regulates the removal of CO2 (and acid)
Change VA
Seconds to minutes (maximal in hours) “fast.”
Three Primary Systems Regulate the [H+] in Body Fluids
3. Kidneys (3)
Excrete an acidic or alkaline urine
Hours to days (maximal in days) “slow.”
Most powerful of the Acid/Base Regulatory Systems
Bicarbonate Buffer System (3)
CO2 + H2O > H2CO3 > H+ HCO3-
Most Powerful EC Buffer
CO2 and HCO3- regulated by respiratory and renal systems
Phosphate Buffer System (4)
H2PO4- > H+ + HPO4-2
Not a significant buffer for ECF
Concentration significantly lower than Bicarbonate system
Important for buffering renal tubular fluids and ICF
60-70% of the total chemical buffering of the body fluids is
inside
the cells
H+ entry into cells: (3)
CO2 Produced: Lactic, acetoacetic, β-hydroxyl- butyric acid H+/K+ exchange (contributes to hyperkalemia)
Intracellular Buffers (2)
1. Proteins Ex. Hb/DeoxyHb 2. Organic Phosphates ATP, ADP, AMP Glucose-1-PO4 2,3-DPG
Intracellular Buffers (2)
1. Proteins Ex. Hb/DeoxyHb 2. Organic Phosphates ATP, ADP, AMP Glucose-1-PO4 2,3-DPG
CO2 =
H+