Acid/Base Balance Flashcards
Why are fetuses more acidic than adults?
There is more CO2 on their side (all oxygen going to mother)
What is the normal pH range for blood?
7.35-7.45
What is the only biological fluid without a narrow range of pH?
Urine
Why can acidosis be fatal?
Arrhythmia occurs and the CNS becomes depressed and normal functioning doesn’t carry on
Types of buffers (x2)
Intracellular and extracellular
Intracellular buffers
- Amino group can consume H+
- Carboxyl group can give up H+
- Both buffer systems can be reversed
Extracellular buffers
Bicarb buffer system!!
Why are the elements of the bicarb system usually present?
Because CO2 and H2O are usually present
In the bicarb buffer system, why doesn’t it stay at carbonic acid?
It is very unstable!!
What happens when there is increases CO2 levels in bicarb buffer?
pH goes down!
Increased CO2 –> increased H2CO3 –> increased H+
Bicarb system explained
CO2 combines with water –> carbonic acid goes up
Carbonic acid decomposes –> H+ and bicarb
**Can be reversed
How is CO2 generated?
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)
After CO2 is made, what 3 things can happen?
- Partakes in bicarb system in capillary plasma (slow)
- Reacts with hemoglobin in RBC to make HbCO2
- Partakes in bicarb system in RBC (fast)
Loss of CO2 at pulmonary capillaries
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
What happens in respiratory acidosis?
Increase of pH due to increased CO2
Causes of respiratory acidosis
Lung damage, loss of airway patency, chest wall damage (muscles of respiration)
Damage/incapacitation (opiate poisoning) of respiratory centres in medulla oblongata
Acute respiratory acidosis can cause…
Sympathetic stimulation
What happens in non-respiratory acidosis?
Increased pH due to increased H+ (not because of CO2 levels)
Causes of non-respiratory acidosis (x7)
- Anaerobic metabolism (lactic acid production)
- Kidney dysfunction (not getting rid of the acid efficiently)
- Incomplete breakdown of fatty acids (seen in diabetes and starvation)
- Consumption of lots of ethanol (turns into acetic acid –> also seen with small amounts of toxic alcohols that poisons the liver
- Ineffective clearance of nonvolatile acids
- Acidic fruits
- Diarrhea (loss of bicarb rich intestinal fluid)
Respiratory causes of alkalosis
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)
Non-respiratory causes of alkalosis
- Vomiting: loss of H+ from stomach contents
- Ingestion of bicarb (laxative)
- Constipation: absorption of extra bicarb from feces (in large bowl for a long time –> more absorption)
Two ways to compensate for changes in pH
- Respiratory: breathe more/less
2. Renal: pee out more/less H+
How does the body sense CO2 and H+ levels?
Peripheral chemoreceptors in aortic arch sense O2 and CO2
Central chemoreceptors in respiratory centres sense CO2
**Drives you to breathe
What is the biggest driver for breathing?
Increased CO2!!
Renal compensation
Too much acid = pee H+
Too much base = pee bicarb
What happens durning long-term compensation of acidosis?
Bicarb gets preserved by using the kidneys
How do you deal with nonvolatile acids?
With the kidneys! (takes hours)
Can’t breathe these acids out
Increased H+ effect on Na+/H+ antiporter in PCT
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
