12: Physiology 8

Question 1

What is the normal pH of the blood?

Answer 1

7.4

Question 2

Which blood vessels have a lower pH?

Answer 2

Veins

more CO2

Question 3

What is the normal blood concentration of bicarbonate ions?

Answer 3

22 - 28

sits around 25

Question 4

What is the normal partial pressure of CO2 in the blood?

Answer 4

40 mmHg

Question 5

What needs to be brought back to normal to

a) compensate for
b) correct

an acid-base imbalance?

Answer 5

a) pH

b) pH, [HCO3-], pCO2

Question 6

What are compensation and correction of an acid-base disturbance?

Answer 6

Compensation - bringing pH back to normal

Correction - bringing pH, [HCO3-] and pCO2

Question 7

What are the four types of acid-base imbalance?

Answer 7

Metabolic acidosis and alkalosis

Respiratory acidosis and alkalosis

Question 8

What solutions are responsible for correcting short-term changes in pH?

Answer 8

Buffers

Question 9

What component of blood acts as a buffer?

Answer 9

Hb

unoxygenated blood has a higher affinity for H+ than oxygenated blood

Question 10

What happens when buffers run out?

Answer 10

Kidney replaces them

Question 11

ph = pk + log(kidneys/lungs)

Question 12

Which organs regulate blood concentration of

a) CO2
b) bicarbonate?

Answer 12

a) Lungs

b) Kidneys

Question 13

What are the normal ranges of concs. for

a) pH
b) bicarbonate?

Answer 13

a) 7.35 - 7.45 (normal is 7.4)

b) 22 - 28 (normal is 25)

Question 14

What general group of diseases causes CO2 retention?

Answer 14

Respiratory disease

Question 15

CO2 retention causes an (increase / decrease) in the concentrations of which ions?

Answer 15

H+ (importantly)

HCO3-

shifts equilibrium to the right and causes acidosis

Question 16

Can buffer solutions buffer themselves?

Answer 16

No

So an increase in CO2 causes both H+ and HCO3 to increase, but HCO3 doesn’t compensate

Question 17

When is respiratory acidosis

a) compensated
b) uncompensated?

Answer 17

a) High CO2, normal pH

b) High CO2, low pH

Question 18

Which system compensates for respiratory acidosis?

Answer 18

Renal

Question 19

What drives bicarbonate reabsorption by the kidneys?

Answer 19

H+ secretion by the kidneys

Question 20

How much bicarbonate is reabsorbed by the kidneys in metabolic acidosis?

Answer 20

All of it

Question 21

What happens to H+ ions after they are excreted into the renal tubules to drive HCO3- reabsorption?

Answer 21

Excreted in urine as titratable acid and ammonium

Question 22

What increases as a result of renal compensation for metabolic acidosis?

Answer 22

[HCO3-] reabsorption

and therefore pH increase

Question 23

After the kidneys have compensated for a metabolic acidosis, how do you correct it?

Answer 23

Restore normal ventilation

Question 24

What are some causes of respiratory alkalosis?

Answer 24

High altitude (conc of oxygen breathed in decreases, rate of body’s removal of CO2 stays the same –> alkalosis)

Hyperventilation

Question 25

What is removed **excessively** in respiratory alkalosis?

Answer 25

**CO2**

Question 26

What happens as a result of excessive CO2 removal in respiratory alkalosis?

Answer 26

**H**+ and **HCO3**- decrease **CO2 starts to increase** equilibrium shifts to the left

Question 27

What system compensates for **respiratory alkalosis**?

Answer 27

**Renal**

Question 28

What happens to H+ secretion in respiratory alkalosis?

Answer 28

**Decreases, as no CO2 to drive it**

Question 29

What happens to bicarbonate reabsorption in metabolic alkalosis?

Answer 29

**Decreases** **As H+ isn't being secreted to drive it**

Question 30

In uncompensated respiratory alkalosis, the urine turns \_\_\_.

Answer 30

**alkaline**

Question 31

How is respiratory alkalosis corrected?

Answer 31

**Restoration of normal breathing**

Question 32

What can cause **metabolic acidosis**?

Answer 32

**Anything causing H+ excess not related to CO2:** Ingestion of acid Increased metabolism of acid (anaerobic resp, uncontrolled T1DM) Loss of bicarbonate - diarrhoea

Question 33

What happens to pH in uncompensated metabolic acidosis?

Answer 33

**pH decreases** **Bicarbonate decreases**

Question 34

Why do bicarbonate levels decrease in uncompensated metabolic acidosis?

Answer 34

**Used up trying to buffer for increased H**+

Question 35

What system compensates for **metabolic acidosis**?

Answer 35

**Respiratory**

Question 36

What senses acidosis with a metabolic cause? How does the respiratory system compensate for metabolic acidosis?

Answer 36

**Peripheral chemoreceptors** (carotid sinus and aorta) ## Footnote **Hyperventilation**

Question 37

How does hyperventilation compensate for metabolic acidosis?

Answer 37

**Blows off Co2**

Question 38

After the resp system has compensated for metabolic acidosis, what happens to bicarbonate levels? How does the renal system correct this?

Answer 38

**Decrease further** (equilibrium shifts to left) **Secretion of H**+ **as acid/ammonium** **Which drives bicarbonate reabsorption**

Question 39

How long do the a) respiratory b) renal systems take to compensate and correct for acid base imbalances?

Answer 39

**a) Short time** **b) Longer**

Question 40

What causes **metabolic alkalosis**?

Answer 40

**Loss of H**+ not related to breathing: **Vomiting** - loss of HCl **Ingestion of alkali** **Hypersecretion of aldosterone** (because K+ and H+ filtration are PAIRED, so H+ is excreted causing an alkalosis)

Question 41

What happens to **pH** and **bicarbonate conc.** in **uncompensated metabolic alkalosis**?

Answer 41

**pH increases** **Bicarbonate conc. increases**

Question 42

How does the resp system compensate for metabolic alkalosis?

Answer 42

**Hypoventilation** retention of CO2, equilibrium shifts to the right

Question 43

How does the renal system correct **metabolic alkalosis**?

Answer 43

**Excess of bicarbonate is filtered** **No acid generated** **Excreted in urine** - alkaline