Acid Base Balance Flashcards
Plasma HCO3 us how much more concentrated then plasma H+
600,000 times (H+ bound to Hb)
How is the relationship between CO2, HCO3 and H+ expressed
CO2 + H20 <—-> H+ + HCO3
Shifts according to law of mass action
Increase CO2 shifts the equation which direction
To right creating one H and one HCO3
Adding H causes equation to shift to what direction
Right
HCO3 acts as buffer resulting in
Increase CO2 + increased H20 <— increased H+ + decreased HCO3
How does ventilation compensate for pH disturbances
Peripheral and central chemoreceptors sense changes in plasma PCO2 and or H+ and signal to respiratory CC to adjust ventilation
What can correct disturbances in acid-base balance as well as cause them
Ventilation
Acidosis causes what kind of ventilation
Hypoventilation - right shift
Decrease plasma CO2
Alkaline state causes what type of ventilation
Hyperventilation- left shift
Increase CO2
What is direct mechanism of kidneys to handle pH disturbances
Altering rates of excretion or reabsorption of H+
- if alkalosis reabsorb H+
- if acidosis secrete H+ for excretion
How do kidneys indirectly handle pH disturbances
Changing rate at which HCO3 buffer is reabsorbed or excreted
- if acidosis buffer excess H+
- is alkaline decrease buffers
During acidosis what do kidneys generally do
Excess H+ is buffered by ammonia within tubule cells or enter lumen and buffered by phosphate
Is not filtered, enters tubule via secretion only
H+
Secretes H+ and reabsorb HCO3
Proximal tubule
First mechanism of secretion of H and reabsorption of HCO3
- Na-H exchanger secretes H
- H in filtrate combines with filtered HCO3 to form CO2
- H+ is secreted again to repeat
- HCO3 is reabsorbed with Na
Secondary mechanism of H+ secretion and HCO3 reabsorption
- Glutamine is metabolized to ammonium and HCO3 2. NH4 is secreted and excreted with H+
What controls acid excretion
Distal nephron, initial portion of collecting duct plays role in fine regulation of acid-base balance
when do type A intercalated cells in collecting duct function
during acidosis
when do type B intercalated cells in collecting duct function
during alkalosis
what do type A cells do
function to increase H+ secretion and HCO3 reabsorption
- usually accompanied by increase in K+ reabsorption (can cause hyperkalemia)
what do type B cells do
function to increase H+ reabsorption and HCO3 secretion (excreted so less buffer)
- usually accompanied by increased K+ secretion (may cause hypokalemia)
what transports H+ on intercalated cells
H+ trasnporters and H-K ATPase
what trasnports HCO3 on intercalated cells
HCO3/Cl exchanger
what are the differences between transporters on type a and type b
Type A has H+ trasnporters on apical and HCO3 on basolateral
Type B has the opposite
what is the range buffers function in
7.38-7.42
