Acid/Base Balance

Question 1

Why are fetuses more acidic than adults?

Answer 1

There is more CO2 on their side (all oxygen going to mother)

Question 2

What is the normal pH range for blood?

Answer 2

7.35-7.45

Question 3

What is the only biological fluid without a narrow range of pH?

Answer 3

Urine

Question 4

Why can acidosis be fatal?

Answer 4

Arrhythmia occurs and the CNS becomes depressed and normal functioning doesn’t carry on

Question 5

Types of buffers (x2)

Answer 5

Intracellular and extracellular

Question 6

Intracellular buffers

Answer 6

• Amino group can consume H+
• Carboxyl group can give up H+
• Both buffer systems can be reversed

Question 7

Extracellular buffers

Answer 7

Bicarb buffer system!!

Question 8

Why are the elements of the bicarb system usually present?

Answer 8

Because CO2 and H2O are usually present

Question 9

In the bicarb buffer system, why doesn’t it stay at carbonic acid?

Answer 9

It is very unstable!!

Question 10

What happens when there is increases CO2 levels in bicarb buffer?

Answer 10

pH goes down!

Increased CO2 –> increased H2CO3 –> increased H+

Question 11

Bicarb system explained

Answer 11

CO2 combines with water –> carbonic acid goes up

Carbonic acid decomposes –> H+ and bicarb

**Can be reversed

Question 12

How is CO2 generated?

Answer 12

Metabolically active cells constantly make CO2

This CO2 enters capillary plasma to partake in bicarb buffer system (very slow)

Rest of the CO2 enters the RBCs to combine with hemoglobin –> HbCO2

Some of CO2 partakes in bicarb buffer system in the RBC (very fast; carbonic anhydrase)

Question 13

After CO2 is made, what 3 things can happen?

Answer 13

1. Partakes in bicarb system in capillary plasma (slow)
2. Reacts with hemoglobin in RBC to make HbCO2
3. Partakes in bicarb system in RBC (fast)

Question 14

Loss of CO2 at pulmonary capillaries

Answer 14

CO2 goes down conc. gradient from blood –> lungs

HCO3- converts into CO2 and H2O (slow in plasma, fast in RBC)

HbCO2 also gives up its CO2

**Everything leaves to alveolar air so pH increases

Question 15

What happens in respiratory acidosis?

Answer 15

Increase of pH due to increased CO2

Question 16

Causes of respiratory acidosis

Answer 16

Lung damage, loss of airway patency, chest wall damage (muscles of respiration)

Damage/incapacitation (opiate poisoning) of respiratory centres in medulla oblongata

Question 17

Acute respiratory acidosis can cause…

Answer 17

Sympathetic stimulation

Question 18

What happens in non-respiratory acidosis?

Answer 18

Increased pH due to increased H+ (not because of CO2 levels)

Question 19

Causes of non-respiratory acidosis (x7)

Answer 19

1. Anaerobic metabolism (lactic acid production)
2. Kidney dysfunction (not getting rid of the acid efficiently)
3. Incomplete breakdown of fatty acids (seen in diabetes and starvation)
4. Consumption of lots of ethanol (turns into acetic acid –> also seen with small amounts of toxic alcohols that poisons the liver
5. Ineffective clearance of nonvolatile acids
6. Acidic fruits
7. Diarrhea (loss of bicarb rich intestinal fluid)

Question 20

Respiratory causes of alkalosis

Answer 20

Caused by low CO2 in blood

Hyperventilation: excessive amounts of deep breathing (drives down alveolar CO2 so blood compensates for that –> blood loses CO2 –> increased pH)

Question 21

Non-respiratory causes of alkalosis

Answer 21

1. Vomiting: loss of H+ from stomach contents
2. Ingestion of bicarb (laxative)
3. Constipation: absorption of extra bicarb from feces (in large bowl for a long time –> more absorption)

Question 22

Two ways to compensate for changes in pH

Answer 22

1. Respiratory: breathe more/less

2. Renal: pee out more/less H+

Question 23

How does the body sense CO2 and H+ levels?

Answer 23

Peripheral chemoreceptors in aortic arch sense O2 and CO2

Central chemoreceptors in respiratory centres sense CO2

**Drives you to breathe

Question 24

What is the biggest driver for breathing?

Answer 24

Increased CO2!!

Question 25

Renal compensation

Answer 25

Too much acid = pee H+

Too much base = pee bicarb

Question 26

What happens durning long-term compensation of acidosis?

Answer 26

Bicarb gets preserved by using the kidneys

Question 27

How do you deal with nonvolatile acids?

Answer 27

With the kidneys! (takes hours)

Can’t breathe these acids out

Question 28

Increased H+ effect on Na+/H+ antiporter in PCT

Answer 28

With this antiporter, Na+ enters the PCT cell and H+ enters the filtrate

This system takes a while (antiporters have to be made)

Once Na+ leaves to the capillary through Na+/K+ pump, bicarb can leave via a bicarb facilitated diffusion transporter –> more basic now

**You never waste bicarb in the kidneys