Renal regulation of H+

Question 1

What is the normal pH range of ECF

Answer 1

7.35-7.45

Question 2

Why is body pH control so important

Answer 2

protein function is dependent on pH

Question 3

How is pH of a solution determined

Answer 3

By the hydrogen ion concentration in the solution

Question 4

Is ICF more or less acidic than ECF

Answer 4

ICF is more acidic as its normal pH is around 7.2

Question 5

What are chemical buffers

Answer 5

Chemicals that bind to H+ and remove it from the solution if it’s acidic or release H+ into the solution if basic

Question 6

What is the protein buffer system

Answer 6

Amino acids bind to H+

Question 7

What is the Bicarbonate buffer system

Answer 7

CO2 + H20 can become H2CO3 ( carbonic acid ) which can H + HCO3 ( bicarbonate ).
And vice versa

Question 8

List the two chemical buffer systems in the body

Answer 8

Protein buffer system and Bicarbonate buffer system

Question 9

How do physiological systems stabilize pH via the renal system

Answer 9

using acids or bases

Question 10

How do physiological systems stabilize pH via the respiratory system

Answer 10

using volatile acids including CO2. excess H+ will cause lungs to expel a lot of CO2 as H+ is converted to CO2

Question 11

Compare the Renal vs Respiratory buffering methods

Answer 11

Renal : greater buffering capacity but effect takes several hours or a day
Respiratory : can only excrete volatile acids but effect happens within minutes

Question 12

What happens if one of the buffering systems breaks down

Answer 12

The other system will compensate but it is not ideal

Question 13

Where are the two physiological buffering systems in the body

Answer 13

The renal and respiratory system

Question 14

Describe the normal control of pH mechanism in the renal system ( Hint: 6 steps )

Answer 14

1- HCO3 & H+ are filtered at the glomerulus
2- HCO3 in filtrate combines with H+ to make H2CO3
3- dissociates into H20 and CO2 both then diffuse into tubular cells
4- H2O and CO2 recombine into H2CO3 and then dissociate into HCO3 and H+ in the tubular cells
5- HCO3 is diffused into the blood and H+ is secreted into the filtrate
6- H+ combines with more HCO3 in the filtrate and cycle starts again

Question 15

Where is 85% of the HCO3 filtered

Answer 15

PCT

Question 16

Where is 10% of HCO3 filtered

Answer 16

DCT

Question 17

Where is 5% of HCO3 filtered

Answer 17

Collecting Ducts

Question 18

Is any of HCO3 excreted and explain why or why not

Answer 18

None of the HCO3 is excreted. The purpose of filtration is to get rid of some of the H+ but the HCO3 should be kept in the body

Question 19

What happens to H+ in the nephron

Answer 19

It is constantly being reabsorbed and then secreted again. most gets secreted again and that’s why urine is acidic

Question 20

What is the normal pH is secretion of H+ is higher than reabsorption

Answer 20

Urine pH is between 4.5 - 7.4

Question 21

Describe the renal correction of acidosis ( pH < 7.35 )

Answer 21

1- Excess H+ in filtrate
2- all available HCO3 combines with H+
3- Excess CO2 in filtrate will be reabsorbed
4- H20 and CO2 recombine to make H2CO3 that dissociates into HCO3 and H+ in the tubular cells
5- HCO3 diffuses into blood to increase pH and H+ excreted into filtrate
6- no more HCO3 so excess H+ will be excreted into urine , cycle won’t start again as normal

Question 22

How is H+ buffered in the urine

Answer 22

PH below 4.5 will stop H+ secretion and limit reabsorption of HCO3
1- NH3 will be secreted by tubular cells into the filtrate
2- H+ will combine with NH3 to make NH4+
3- NH4+ can’t be reabsorbed so H+ will be excrete in urine

Question 23

What is the physiological effect of a drop in PH

Answer 23

1- effects binding of calcium to plasma protein since H+ binding to albumin then there will be more free calcium ions
2- Calcium ions block sodium channels and reduces their opening
3- AP firing in myocytes and nerves is reduced
4- membrane potential of excitable cells will stabilize and they’ll be harder to stimulate

Question 24

What conditions can result from a drop in Ph ( Hint: 3 )

Answer 24

1- Cardiovascular depression : bradycardia followed by asystole
2- CNS depression : stupor followed by coma
3- reduced muscle contraction

Question 25

Describe what respiratory acidosis is and what can cause it

Answer 25

Causes : Can happen due to ventilatory failure or severe ventilatory defects ( ex: COPD )
Effect : high levels of CO2 and may have low O2 level. Slightly lower pH. Raised plasma HCO3 by the renal system to combat respiratory acidosis.

Question 26

List the causes of Metabolic acidosis (Hint : 6)

Answer 26

Cause :
1- Renal injury / disease causing less H+ secretion and HCO3 reabsorption.
2- Aspirin overdose
3- Diabetic Ketoacidosis
4- Alcoholism causing kidney inflammation
5- Diarrhoea causes loss of sodium which effects H+ secreted
6- Addison’s disease causes less H+ secretions because hypoaldosteronism

Question 27

Describe biochemical effects in blood of metabolic acidosis

Answer 27

1- Low pH and Low ECF bicarbonate
2- normal PaO2 levels and PaCO2 levels
3- If there is compensatory deep breathing then CO2 might decrease
4- H+ levels go up and HCO3 goes down which causes an anion gap that will lead to metabolic acidosis

Question 28

What is Kussmaul’s breathing

Answer 28

Deep breathing removing excess CO2

Question 29

Explain the renal correction of alkalosis mechanism ( pH> 7.5 )

Answer 29

1- Reduced level of H+ in filtrate means less H2CO3 formed in tubular lumen
2- Less CO2 and H20 formed and reabsorbed
3- Reduction in HCO3 reabsorbing = reducing oh H+ secretion
4- surplus of HCO3 will be excreted
5- Body will create more H+ so plasma pH can increase

Question 30

What is the physiological effect of uncompensated alkalosis

Answer 30

1- Rising PH will result in less H+ binding to albumin
2- Ca binding to albumin will increase and relieve NA channels , increasing their opening
3- AP firing in myocytes and nerves is increased so excitable cells will depolarized more easily

Question 31

What conditions can result from uncompensated alkalosis ( hint: 3 )

Answer 31

1- Confusion ( brain problems )
2- Skeletal muscle spasms ( ex: diaphragm)
3- Death if not rectified

Question 32

What can cause Respiratory Alkalosis

Answer 32

1- Hyperventilation : decrease PaCO2 and HCO3 so renal system won’t absorb HCO3

Question 33

What causes Metabolic acidosis

Answer 33

1- Bicarbonate overdose ( antacid ) : HCO3 and PaCO2 levels increase
2- Hyperaldosteronism : increase H+ secretion
3- Vomiting : loosing gastric acids

Question 34

If acidosis is coupled with low level of HCO3 then what does that signal and how is it compensated

Answer 34

Metabolic Acidosis. Compensated by Respiratory expulsion of CO2 from lungs.

Question 35

If acidosis is coupled with increase of PCO2 levels what does that signal

Answer 35

Respiratory acidosis. Compensated via renal by increase of HCO3 levels

Question 36

If there is respiratory alkalosis what will happen to concentration of CO2 in blood and how is it compensated

Answer 36

It will decrease and Renal will compensate by decreasing HCO3 levels

Question 37

If there is Metabolic alkalosis what will happen to HCO3 concentration and how is it compensated

Answer 37

it will increase and will be compensated via respiratory by increasing CO2 levels