regulation of homeostasis by the kidney - acid base balance Flashcards
what is role of the kidney in volume regulation
fluid balance - amount of water gained by body equals lost
electrolyte blance - loss=gain
how is acid-base balance controlled by the kidneys
H+ gain is offset by H+ loss
why is pH control important
pH of ECF remains between 7.35 and 7.45
outside these boundaries can effect all body systems - coma, cardiac failure, circulatory collapse (<6.8, >8 = death)
what are acids and bases
acid - add H+ into solution
base removes them
acids and bases strong or weak
ph= potential of H+, acidity or basicity of aq solution
what are buffers
resist change in pH by restoring H+ balance types carbonic acid/bicarbonate protein phosphate
how are kidneys important to homestasis
essential to maintaining acid base balance as all biochemical processes occur in optimal pH window (7.2-4)
done with cardiovascular system and respiratory system
how does the body regulate pH
lungs CO2 + H20 = H2CO3 = H+ + HCO3- kidneys
lung and kidney sec acid (pot acid and non volatile acids res)
all filtered HCO3- reabs as physiological buffer
prevents acidosis or alkalosis
via carbonic anhydrase
middle - carbonic acid (volatile)
what is the relationship between pH, HCO3- and CO2
pH = HCO3-/CO2
physiological buffer over potential acid (H2CO3)
blood ph 7.4, urine 6
blood HCO3- 24mM and pCO2 40mmHg
plasma osmolarity 285 mOsm/kg water, urine 600
depend on hydration
how does HCO3- affect CO2
INVERSE relationship
one up, other goes down
CO2 inc, pH dec (CO2 + H20 - carbonic acid)
balances to stop acidosis (inc CO2) and alkalosis (dec CO2)
What detects pH changes
peripheral chemoreceptors, act on resp centres in brain to adjust resp rate to alter CO2 and pH
eg hyper and hypo ventilation
how are the kidneys important in acid base regulation
HCO3 filt and reabs, H+ sec in PT RTA can occur more H sec and HCO3 reabs to inc pH sec of H+ inhibited when urine falls below 4.5 pH opposite when ph of ECF inc
what does the DT and CD do for acid base balance
H+ sec
HCO3- reabs
HCO3- generation (from AAs and exchanged with cl-)
intercalated celleas
what is acidosis
pH of body fluids falls below 7.35
too much H+ so need to remove it
excrete via lungs as CO2 and kidneys
generate more buffer in kidneys
what is alkalosis
opposite of acids
reduce CO2 excretion in lungs
inc excretion of HCO3- in kidneys
inc H+ generation by kidneys
what are the types of acidosis
respiratory (inadequate ventilation, acute or chronic)
metabolic (all conditions other than lungs that dec pH, chronic)
only chronic sig affect HCO3-
from CO2 in blood, non volatile acids from metabolism, loss of HCO3- in diarrhoea and non gastric GI fluids, loss of HC03- in urine