Lecture 9: Renal & Respiratory Compensation

Question 1

how does metabolic alkalosis affect pH and [HCO3-]

Answer 1

increases pH
increases [HCO3-]

Question 2

how does metabolic acidosis affect pH and [HCO3-]

Answer 2

decreases pH
decreases [HCO3-]

Question 3

what is the effect of compensation in response to metabolic alkalosis

Answer 3

increases PCO2

Question 4

what is the effect of compensation in response to metabolic acidosis

Answer 4

decreases PCO2

Question 5

what is the effect of respiratory alkalosis on pH and PCO2

Answer 5

pH increases
PCO2 decreases

Question 6

what is the effect of respiratory acidosis on pH and PCO2

Answer 6

pH decreases
PCO2 increases

Question 7

what is the effect of compensation in response to respiratory alkalosis

Answer 7

decreases [HCO3-]

Question 8

what is the effect of compensation in response to respiratory acidosis

Answer 8

increases [HCO3-]

Question 9

what 3 mechanisms help keep plasma pH within a narrow range

Answer 9

• buffers
• respiratory response
• renal response

Question 10

when blood gases and or pH change, _________ trigger changes in ventilation (tidal volume and breathing rate)

Answer 10

chemoreceptors

Question 11

what do brainstem receptors monitor

Answer 11

CO2 and pH

Question 12

what do peripheral receptors monitor

Answer 12

O2, CO2, pH

Question 13

Carotid and aortic bodies monitor ??

Answer 13

O2, CO2, pH
b/c they are peripheral chemoreceptors

Question 14

how do glomus cells respond when O2 tension or pH decreases, or when CO2 increases

Answer 14

depolarize

Question 15

a decrease in PaO2 below ____-_____mmHg causes carotid and aortic bodies to stimulate respiration

Answer 15

60-70

Question 16

central chemoreceptors monitor _____

Answer 16

CO2 (and pH)

Question 17

how does CO2 effect breathing

Answer 17

CO2 crosses BBB
increases H+ ion concentration in brain interstitial fluid, activating central chemoreceptors

Question 18

what happens to breathing rate if pH decreases in CSF

Answer 18

breathing increases

Question 19

what happens to breathing rate if pH increases in CSF

Answer 19

breathing rate decreases

Question 20

how doe the kidneys excrete an acid load?

Answer 20

1. bicarbonate reabsorption
2. titratable acidity
3. ammonia genesis and NH4+ excretion
4. bicarbonate secretion if available in excess

Question 21

where in the tubular system is H+ secreted

Answer 21

proximal tubule

Question 22

is bicarbonate freely filtered?

Answer 22

yes

Question 23

bicarbonate uptake is dependent on the activity of _______ in the cell ?

Answer 23

carbonic anhydrase

Question 24

within the cell, ______ facilitates the generation of H+ and HCO3-

Answer 24

CA-II

Question 25

what is the most important transporter in the PT

Answer 25

Na/H+

Question 26

what facilitates the production of water and CO2 from luminal carbonic acid

Answer 26

membrane bound carbonic anhydrase

Question 27

how does HCO3- exit the cell

Answer 27

by crossing the basolateral membrane

Question 28

what are the steps of bicarbonate reabsorption

Answer 28

1. w/in the cell, CA-II facilitates the generation of H+ and HCO3- 2. H+ is secreted into tubular fluid 3. membrane-bound CA facilitates production of water and CO2 from luminal carbonic acid 4. membrane permeable for CO2 5.HCO3- exits cell across basolateral membrane

Question 29

what are the 3 transporters in the apical membrane of epithelial cells that secrete protons

Answer 29

- Na+/H+ exchanger - H+ATPase - K+/H+ ATPase

Question 30

where in the tubular system is HCO3- reabsorbed

Answer 30

Collecting Duct

Question 31

what is titratable acidity

Answer 31

1. kidney excretes H+ w/ urinary buffers like phosphate and urate - secreted protons bound to buffer ions are retained in tubule fluid then excreted 2. a "new HCO3-" is generated

Question 32

how does ammoniagenesis and NH4+ excretion occur

Answer 32

1. kidney metabolizes glutamine 2. NH4+ is excreted or returned to blood 3. HCO3- is returned to the blood as "new HCO3-"

Question 33

3 steps of ammonium excretion

Answer 33

1. PT: ammoniagenesis enables bicarbonate production and absorption; NH4+ is transported into tubule fluid 2. TAL: NH4+ is reabsorbed by Na/K/2Cl co-transporter (medullary recycling) 3. CD: ammonia trapping - High NH3/NH4+ concentrations in medullary interstitium favors excretion

Question 34

renal removal of NH4+ is enhanced by ________ in dogs, chickens, rats and mice but not in cats or rabbits

Answer 34

acidosis

Question 35

how do the kidneys excrete a load of [H+] or replace a bicarbonate deficit?

Answer 35

- reabsorption of all filtered bicarbonate - additional H+ secreted via H+ATPases attached to bases (either titratable acids or via glutamine metabolism)

Question 36

in the cortical CD, what type of cells contain H+ATPase in the basolateral plasma membrane

Answer 36

type B intercalated cells

Question 37

type B intercalated cells are rich in ______ ?

Answer 37

cytoplasmic carbonic anhydrase

Question 38

what exchanger is in the apical plasma membrane of the CD and mediates HCO3- secretion

Answer 38

Cl-/HCO3-, pendrin

Question 39

what is the pendrin transporter (Cl/HCO3-) dependent on

Answer 39

sufficient Cl levels - low Cl levels can cause impairment of bicarbonate secretion by type B intercalated cells -----> metabolic alkalosis

Question 40

Renal response to Alkalosis results in a reduction of ______ excretion and an increase in _______ secretion

Answer 40

reduced acid (NH4+) excretion increased bicarbonate secretion

Question 41

renal response to Acidosis results in the reduction/elimination of all _______ from urine and promotes ______ secretion

Answer 41

elimination of HCO3- from urine acid secretion