36, 41 & 51: Acid Base Physiology Flashcards
What are the two main ways acids are produced in the body?
- Oxidative metabolism (volatile acids)
- Protein catabolism (non volatile acids)
What are the two non volatile acids?
Sulfuric acid (oxidation of sulfur containing AA residues) Phosphoric acid (catabolism of phospholipids)
Non volatile acids increase markedly in ____ and ____
Anaerobic metabolism and insulin deficiency
What are the buffer systems in the body?
- Bicarbonate buffer system
- Blood buffer system
- Intracellular proteins and organic phosphates in red cells, tissue and bone
Why is the bicarbonate buffer much more effective than proteins and organic phosphates in bone etc?
Bicarbonates contained in much higher ECF concentrations
What is the isohydric principle?
pH can be evaluated from the status of any buffer system as they are all in equilibrium
How are volatile acids buffered?
Blood
How are non-volatile acids buffered?
Bicarbonate buffer
Explain the blood buffer
- CO2 diffuses into RBC
- converted via carbonic anhydrase carbonic acid
- Dissociates into HCO3 and H
- RBC membrane impermeable to H+ so retained and used to form carbamino haemoglobin
- Facilitates oxygen release
Why is hypoxia a potent stimulus for ventilatory drive?
Peripheral chemoreceptors (aortic and carotic bodies) very sensitive to oxygen
Describe how bicarbonate is reabsorbed/regenerated by the kidney
Proximal tubule
- H+ exchanged for Na
- H+ reacts with bicarbonate
- CO2 diffuses into cell
- Forms bicarbonate ions, reabsorbed
Why does renal acid excretion take the longest?
Dependent on stores of ammonia and phosphate ions
Bicarbonate reabsorption in the kidney is directly related to ____ and inversely related to plasma __ and __
- Directly related to PaCO2
- Inversely related to K and Cl
What causes an increased anion gap?
Inc. production of non-volatile acids which don’t have Cl- as the anion (lactate, beta hydroxybutyrate)
What are the two main things that can reduce exchange of oxygen?
- Inc. PCO2
- Impaired diffusion
