Acid-base Flashcards
Features of alkalosis?
- pH?
- When does it occur?
- pH > 7.45 (35nmol/L H+)
- CNS: drowsy, headache, tetany convulsions
- Occurs when acid is flushed out of the system (i.e vomiting)
Features of acidosis
- pH?
- When does it occur?
- pH < 7.35 (45 mol/L H+)
- CNS: respiratory disfunction, drowsiness, progressing to coma
- Occurs when bicarbonate is flushed out of system (ie diarrhoea)
What is the pH of the following:
- ECF (blood)
- Cell pH
- Pancreatic fluid
- Gastric acid
- ECF = tightly regulated b/w 7.35-7.45
- Cell pH = 7.1
- Pancreatic fluid = 7.8
- Gastric acid = 1
Why regulate pH?
- What does it influence?
- What does it regulate?
- What does it do for cells?
1) Influences enzyme activity
2) Regulates ion transport mechanisms
3) Cells - metabolism, DNA synthesis, growth
4) CNS (alkalosis & acidosis)
Sources of H+ gain?
- What is it generated from?
- Production of what?
- How is H+ gained?
- Generation of H+ from CO2
- Production of nonvolatile acids from the metabolism of proteins & other organic molecules
- Gain of H+ due to loss of HCO3- in diarrhoea or other non gastric GI fluids
Sources of H+ loss?
How?
- Utilization of H+ in the metabolism of various organic anions
- Vomit
- Urine
- Hyperventilation
What is the equilibrium equation for CO2 in the body?
- CO2 + H2O H2CO3 H+ + HCO3-
* carbon dioxide + water carbonic acid Hydrogen ions + bicarbonate
Why do we need to remove CO2 from the body?
To reduce the potential amount of acid produced
What is the main buffer of H+ in transit? What are its two forms for this interaction?
- Haemoglobin
- Takes up H+ in cells (HHb)
- Releases H+ in lungs (O2Hb-)
The H+ in the lungs then goes on to form CO2
Why is it important to breathe continuously/exhale CO2 to match metabolic production rate?
- To maintain pH levels, otherwise:
1. Hypoventilation –> acidosis (not enough CO2 removed)
2. Hyperventilation –> alkalosis (too much CO2 removed)
What are the 3 main buffers in the body?
- Bicarbonate
- Protein
- Posphate
What is the purpose of the buffers in the body?
Prevent pH from falling to dangerous levels
How does the kidney handle bicarbonate levels? (3 ways)
- Reabsorption of filtered bicarbonate
- Replacement of bicarbonate consumed in excretion of non-volatile acids
- Excretion of excess bicarbonate
How much bicarbonate is lost/excreted when it’s balanced in the body?
None
How is filtered bicarbonate reabsorbed in the body?
Step 1 (think) - What catalyses the formation of carbonate? - What is carbonate formed from? - Where is the carbonate catalysed? Step 2 - What does carbonate dissociate into? Step 3 - Where is the bicarbonate absorbed? - Where are the H+ ions secreted? Step 4 - How/where is carbonate formed? - What is carbonate secreted as?
- Carbonic anhydrase catalyses the formation of carbonate from CO2 and H2O in the epithelial cells
- The carbonate dissociates into H+ ion and bicarbonate
- The bicarbonate is absorbed into the interstitial fluid
- The H+ ions are secreted into the lumen (coupled with Na+)
- The H+ ions combine with bicarbonate in the filtrate to form carbonate, which is secreted as H2O and CO2
Note: no new bicarbonate is formed
