Lecture 19 Renal Acid Base Regulation Flashcards
acid
compounds that release H+ ions
strong acid
completely dissociates
weak acid
incompletely dissociates
volatile acids
acids excreted from lungs (i.e. CO2)
nonvolatile acids
acids excreted from the kidneys (i.e. phosphoric, sulfuric, keotacids, lactic acids)
what is the pH range for venous blood?
7.35-7.45
what is the pH range for arterial blood
7.37-7.44
what are the systems in the body that regulate pH
chemical acid base buffer systems in body fluids
respiratory system
kidneys
buffer
substance that can reversibly bind to H+
buffer systems
bicarbonate buffer system
phosphate buffer system
protein buffers
which buffer system is the most important extracellular system?
bicarbonate
bicarbonate buffers system
consists of a weak acid and a bicarbonate salt
mainly regulated by the kidneys
addition of a strong acid to bicarbonate buffers system
leads to the formation of a weak acid
(strong acid + HCO3- –> H2CO3 –. CO2
addition of strong base to bicarbonate buffer system
leads to the formation of weak base
what organ is the primary regulator of the bicarbonate buffer?
the kidneys
metabolic acid base disorders
primary change in [bicarbonate] in extracellular fluid
metabolic acidosis
decrease in HCO3 - in fluid
metabolic alkalosis
increase in HCO3- in fluid
respiratory acid base disorders
result from a primary change in CO2 in blood
respiratory acidosis
increase in CO2
respiratory alkalosis
decrease in CO2
pH point for bicarbonate buffer and the pKa
the normal pH is 7.4 so there is 20x as much bicarbonate buffer in system in form of HCO3 than CO2
what is the pKa of bicarbonate buffer?
6.1
what is the primary method for removing nonvolatile acids?
renal excretion
what must happen before filtered bicarbonate is reabsorbed
must react with H+ to form carbonic acid
three mechanisms for kidneys to regulate H+
- reabsorb filtered bicarbonate ions
- secrete hydrogen ions
- produce new bicarbonate ions
bicarbonate ion is reabsorbed in which part of kidney
proximal tubule
where does H+ secretion vie PRIMARY active transport occur
intercalated cells of late distal tubule
where does H+ secretion via SECONDARY active transport occur
all parts of tubule except ascending and descending thin limbs
describe bicarbonate ion reabsorption
H+ + HCO3 form carbonic acid
carbonic acid breaks down to form CO2 and H20
CO2 goes to tubular cells and forms carbonic acid after combining with water
carbonic acid breaks down to H+ and HCO3-
bicarbonate ion diffuses from basolateral membrane into intersistial fluid then blood
carbonic anhydrase
from carbonic acid from CO2 and water
necessary for bicarbonate reabsorption
how is bicarbonate normally titrated?
each time a H+ ion is formed there is a bicarbonate formed and released in the blood
how is bicarbonate titrated in acidosis
new bicarbonate ion is added to extracellular fluid
how is bicarbonate ion titrated in alkalosis
bicarbonate ions are removed from ECF via renal excretion
how do the kidneys handle excess base
reabsorbs all the filtered bicarbonate ions (same as adding H+ to ECF) so that the fluid returns to normal
how do lungs cause acidosis? compensatory method?
increase [CO2]
compensate by increasing plasma bicarbonate via addition of new bicarbonate from kidney
how do lungs cause alkalosis? compensatory method?
decrease [CO2] (hyperventilation)
compensate by decreasing plasma bicarbonate via renal excretion
