regulation of homeostasis by the kidney - acid base balance

Question 1

what is role of the kidney in volume regulation

Answer 1

fluid balance - amount of water gained by body equals lost

electrolyte blance - loss=gain

Question 2

how is acid-base balance controlled by the kidneys

Answer 2

H+ gain is offset by H+ loss

Question 3

why is pH control important

Answer 3

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)

Question 4

what are acids and bases

Answer 4

acid - add H+ into solution
base removes them
acids and bases strong or weak
ph= potential of H+, acidity or basicity of aq solution

Question 5

what are buffers

Answer 5

resist change in pH by restoring H+ balance 
types
carbonic acid/bicarbonate
protein 
phosphate

Question 6

how are kidneys important to homestasis

Answer 6

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

Question 7

how does the body regulate pH

Answer 7

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)

Question 8

what is the relationship between pH, HCO3- and CO2

Answer 8

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

Question 9

how does HCO3- affect CO2

Answer 9

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)

Question 10

What detects pH changes

Answer 10

peripheral chemoreceptors, act on resp centres in brain to adjust resp rate to alter CO2 and pH
eg hyper and hypo ventilation

Question 11

how are the kidneys important in acid base regulation

Answer 11

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

Question 12

what does the DT and CD do for acid base balance

Answer 12

H+ sec
HCO3- reabs
HCO3- generation (from AAs and exchanged with cl-)
intercalated celleas

Question 13

what is acidosis

Answer 13

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

Question 14

what is alkalosis

Answer 14

opposite of acids
reduce CO2 excretion in lungs
inc excretion of HCO3- in kidneys
inc H+ generation by kidneys

Question 15

what are the types of acidosis

Answer 15

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

Question 16

how does the body respond to acidosis

Answer 16

inc ventilation to lose CO2
kidneys sec H+, generate HCO3-
other buffer systems absorb H+

Question 17

treatment of respiratory acidosis

Answer 17

restore ventilation
treat underlying dysfunction or disease
IV lactate soliton (HCO3- buffer in liver)

Question 18

treatment of metabolic acidosis

Answer 18

IV isotonic HCO3-

IV lactate solution (Ringers lactate or Hartman’s solution - converted to HC03- buffer in liver)

Question 19

types of alkalosis

Answer 19

respiratory - hyperventilation, acute or chronic
metabolic - all conditions other than resp, chronic
only chronic causes sig affect on HCO3

Question 20

How can H+ be lost

Answer 20

H+ in metabolism of organic anions
loss of H+ in vomit
loss of H+ in urine
hyperventilation (loss of CO2)

Question 21

How does the body respond to alkalosis

Answer 21

kidneys generate H+ and secrete HCO3-
other buffer systems release H+
lung dec resp rate

Question 22

how is respiratory alkalosis treated

Answer 22

treat underlying cause
breathe into paper bag (inc co2)
give IV Cl- cont solution (HCO3- excretion)

Question 23

how is metabolic alkalosis treated

Answer 23

give electrolytes to replace lost
IV Cl- cont solution
treat underlying disorder

Question 24

causes of respiratory acidosis

Answer 24

reduced CO2 elimination
asphyxia 
hypoventilation 
advanced asthma
sev emphysema

Question 25

causes of metabolic acidosis

Answer 25

HC03- elimination
fatty acid and acidic metabolite production (eg KBs in DM)
bad O2 delivery

Question 26

causes of respiratory alkalosis

Answer 26

reduced CO2 in extracellular fluid

dec atm pressure

Question 27

causes of metabolic alkalosis

Answer 27

H+ elimination and HCO3- absorption

ingestion of alkaline substances