Acid Base Balance Part 1 Flashcards
What size of pH change means a large change in body function?
Small pH changes
What physiologic effects to fluctuations in H+ have? (3)
- Excitability of muscle & nerve
- Enzyme activities
- K+ levels
What is the normal pH value in: (4)
Gastric secretions
Cerebrospinal fluid
Pancreatic secretions
Final urine
Gastric secretions 0.7
Cerebrospinal fluid 7.3
Pancreatic secretions 8.1
Final urine 5.4
What systems are involved in pH changes? (3)
- Blood & tissue buffers – seconds
- Respiration – minutes
- Renal – hours/days
What does a buffer do?
Minimise changes in pH
Where can you find buffers in the body? (4)
Blood - Plasma & RBCs (red blood cells)
Extracellular fluid
Intracellular fluid
Urine
What are examples of buffers in the body? (4)
Haemoglobin
HCO-3
Inorganic phosphate
Weak acids/bases on proteins
What is the Henderson Hasselbalch equation?
pH = pK + log [HCO3]/[H2CO3]
pH = 6.1 + log 20/1 (usually) = 7.4
What is the primary ECF buffer and the equation for it? (2)
Carbonic acid/bicrarbonate
CO2 + H2O <–> H2CO3 <–> H+ + HCO3
How does the davenport diagram( HCO-3/pH) change in respiratory acidosis (more CO2)?
Adding CO2 shifts PH to the right, low PH with high bicarbonate concentration
How does the davenport diagram( HCO-3/pH) change in respiratory alkalosis (less CO2)?
If we breathed out more CO2
Shifts to left, low bicarbonate high PH
How does the davenport diagram( HCO-3/pH) change in metabolic acidosis (more H+)?
Excess H+ ions added to system,
Only some of excess H+ bind to bicarbonate
Low Ph with low bicarbonate
How does the davenport diagram( HCO-3/pH) change in metabolic acidosis (more H+)?
Adding bicarbonate
Ph increases
High Ph , High bicarbonate
Which chemoreceptors have chemical control of ventilation in a negative feedback system? (2)
Peripheral and Central chemoreceptors
What do Hypoxia, hypercapnia, Acidosis do? (3)
Hypoxia O2 falls (Increases ventilation)
Hypocapnia CO2 goes up (increases ventilation)
Acidosis if PH falls (increases ventilation)
