7. Renal Control Mechanisms and Acid-Base Disorders

Question 1

Renal control mechanism (5)

Answer 1

1) Only kidneys can remove (rather than bind) acids and bases from the body

2) Slower-acting

3) Hours to days to have impact

4) Much larger impact on the pH level in the blood

5) Main method to manage acid-base imbalance

Question 2

Renal control mechanisms - Primary actions

Answer 2

1) Hydrogen ion secretion
a) Through renal filtrate
b) Occurs in response to pH of extracellular fluid
c) Renal peritubular capillaries allow for reabsorption and secretion between blood and nephron

2) Conversion of bicarbonate ion
a) Most important anion in chemical buffering of extracellular fluid
b) Bicarbonate ions can be replenished in fluid by reclaiming from filtrate
c) In alkalosis, renal collecting duct cells can secrete bicarbonate while recovering H+ to lower the pH of the blood

Question 3

Normal Blood Serum Levels (3)

Answer 3

1) Normal pH - 7.35-7.45

2) Normal PCO2 = 35-45 mmHg (pressure)

3) Normal HCO3 = 22-26 mEq/L (bicarbonate ion concentration - milliequivalents/liter

Question 4

Acidosis (2)

Answer 4

1) Acidosis (blood pH < 7.35)

2) Severe acidosis
a) pH drops below 7.0
b) CNS becomes depressed
c) Without interventions causes coma and death

Question 5

Alkalosis (2)

Answer 5

1) Alkalosis (blood pH > 7.45

2) Severe alkalosis
a) pH rises above 7.8
b) CNS becomes too excited
c) Causes extreme nervousness, uncontrolled muscle contraction, convulsion
d) Without intervention causes death due to cessation of breathing

Question 6

Primary Disorders (2)

Answer 6

1) Metabolic
a) If cellular process in the body are the cause

2) Respiratory
a) If higher or lower CO2 pressure in the blood is the cause

Question 7

Respiratory Acidosis (5)

Answer 7

1) Blood pH < 7.35

2) Due to a higher pressure of CO2
a) PCO2>45mmHg

3) Creates more H+ ions

4) Lowers pH

5) Medical causes
a) Shallow breathing, limited gas exchange
b) Cystic fibrosis, emphysema, pneumonia

Question 8

Respiratory Alkalosis (5)

Answer 8

1) Blood pH > 7.45

2) Due to a lower pressure of CO2

3) Creates less H+ ions

4) Raises pH (more alkaline pH)

5) Medical causes
a) Hyperventilation, such as panic attack

Question 9

Respiratory Acidosis and Alkalosis Compensation (2)

Answer 9

1) Both respiratory disorders cause the renal system to attempt to correct via RENAL COMPENSATION

2) Addition/removal of H+ or bicarbonate ion

Question 10

Metabolic Acidosis (5)

Answer 10

1) pH <7.35

2) HCO3 <22 mEq/L

3) Lower bicarbonate ion centration creates more H+

4) Causes a lower pH

5) Medical causes from buildup of acid metabolic products
a) Alcohol overdose
b) Lactic acid buildup (byproduct of muscular contraction)
c) Extreme diarrhea

Question 11

Metabolic Alkalosis (5)

Answer 11

1) pH > 7.45

2) HCO3 >26 mEq/L

3) Higher bicarbonate ion centration creates less H+

4) Causes a higher pH

5) Medical Causes:
a) Vomiting (loss of stomach acids)
b) Intake of excess antacids
c) Constipation (abnormal retention of HCO3-)

Question 12

Metabolic Acidosis and Alkalosis Correction (2)

Answer 12

1) The body seeks to correct both metabolic disorders through respiratory compensation

2) Increase or decrease the respiratory rate for increased or decreased CO2 levels