T3 L8 Regulation of homeostasis in the kidney: acid-base balance

Question 1

What is the definition of renal dysfunction?

Answer 1

Inability to maintain salt and water balance & acid-base balance

Question 2

What is the role of the kidney in volume regulation?

Answer 2

Fluid balance - amount of water gained by the body = amount lost
Electrolyte balance - ion gain = ion loss

Question 3

Why is pH control important?

Answer 3

Alterations outside the normal range can cause coma, cardiac failure & circulatory collapse
pH < 6.0 or >8.0 leads to death

Question 4

What do acids do?

Answer 4

Release H+ into solution

Question 5

What do bases do?

Answer 5

Remove H+ from solution

Question 6

What is pH?

Answer 6

Potential of hydrogen

Specifies the acidity or basicity of an aqueous solution

Question 7

What are buffers?

Answer 7

Resist changes in pH
When H+ is added, the buffer removes it
When H+ is removed the buffer replaces it

Question 8

What are some types of buffers?

Answer 8

Carbonic acid / bicarbonate
Protein
Phosphate

Question 9

What is the acid-base balance reaction?

Answer 9

CO2 + H2O H2CO3 H+ + HCO3-

Question 10

Why is carbonic acid volatile?

Answer 10

It can be converted to CO2

Question 11

What is the pH of human blood?

Answer 11

7.4

Question 12

What is the pH of urine?

Answer 12

6.0

Slightly more acidic as you get rid of acids through the urine

Question 13

What does urine osmolality depend on?

Answer 13

The hydration status

Question 14

What is the relationship between pH and bicarbonate/CO2?

Answer 14

pH is inversely proportional to (HCO3-) / (pCO2)

HCO3- is a physiological buffer regulated by the kidney
pCO2 is a potential acid that is regulated by the lungs

Question 15

What happens to pH when pCO2 increases?

Answer 15

pH decreases as the extra CO2 reacts with water to form carbonic acid

Question 16

What detects changes in pH?

Answer 16

Peripheral chemoreceptors which act on the respiration centres in the brain to adjust respiration rates

Question 17

What is the most effective regulator of body fluid pH?

Answer 17

Renal system

Question 18

When does renal tubular acidosis occur?

Answer 18

When the kidneys don’t effectively reabsorb HCO3- and secrete H+

Question 19

What happens if the pH of the extracellular fluid increases?

Answer 19

Alkalaemia –> secretion of H+ into filtrate & reabsorption of HCO3- decreases –> extracellular pH decreases

Question 20

What happens if the oH of the extracellular fluid falls?

Answer 20

Acidaemia –> more secretion of H+ into filtrate & reabsorption of HCO3- back into the extracellular fluid –> causes pH to increase

Question 21

What is acidosis?

Answer 21

When the pH of the body fluid falls below 7.35

Too much H+

Question 22

What is the solution to acidosis?

Answer 22

Get rid of H+ out of the body
Excreted via the lungs as CO2 or via the kidneys as H+
Generate more buffer in the kidneys

Question 23

What is alkalosis?

Answer 23

pH of body fluids goes above 7.45

Question 24

What the solution to alkalosis?

Answer 24

Increase H+ levels in the body
Reduce excretion of CO2 via the lungs to increase blood CO2
Increase excretion of HCO3- buffer via the kidneys
Increase generation of H+ by the kidneys

Question 25

What is respiratory acidosis?

Answer 25

Caused by inadequate ventilation

Acute or chronic

Question 26

What is the treatment for respiratory acidosis?

Answer 26

Restore ventilation
Treat underlying dysfunction or disease
Give IV lactate solution which is converted to HCO3- buffer in the liver

Question 27

What is metabolic acidosis?

Answer 27

Results from all conditions that decrease pH apart from respiratory
Always chronic

Question 28

What is the treatment for metabolic acidosis?

Answer 28

Give IV isotonic HCO3-

Give IV lactate solution - converted to. HCO3- buffer in liver

Question 29

What are some ways to gain H+?

Answer 29

CO2 in the blood - combines with H2O to form carbonic acid
Non-volatile acids from metabolism such as lactic acid
Loss of HCO3- in diarrhoea or non-gastric GI fluids
Loss of HCO3- in urine

Question 30

What is respiratory alkalosis?

Answer 30

Caused by hyperventilation

Acute or chronic

Question 31

What is the treatment for respiratory alkalosis?

Answer 31

Treat underlying cause
Breathe into paper bag to increase pCO2
Give IV Cl- containing solution which increases HCO3- excretionn

Question 32

What is metabolic alkalosis?

Answer 32

Results from all conditions that increase pH apart from respiratory
Always chronic

Question 33

What is the treatment for metabolic alkalosis?

Answer 33

Give electrolytes to replace those lost
Give IV Cl- containing solution
Treat underlying disorder

Question 34

What are the reasons for a loss of H+?

Answer 34

Use of H+ in metabolism of organic anions
Loss of H+ in vomit
Loss of H+ in urine
Hyperventilation