Lecture 40 Flashcards
What two parts of the body regulate blood pH? Using what?
pH regulation is done via cooperation between the kidneys and the lungs, this is done using bicarbonate ions which the kidneys can reabsorb (or H+). It is also vaguely ddone via the mouth, skin, stomach and brain.
What is an acid, base, buffer and pH?
An acid releases H+ ions. A base takes up H+ ions. A buffer is substances or mechanisms that act to minimise changes in pH when H+ concentration is altered. pH = -log [H+] (urine pH typically between 4.5-8 depending on diet (lower with more protein).
What is the blood pH normally, what happens if it is different and why is it important?
pH in the blood is normally 7.4, if it is below 7.35 this is known as acidosis, if it is above 7.45 it is alkalosis. (Below 7 or above 7.8 is typically lethal). This is important because pH influences enzyme activity, it regulates ion transport mechanisms, is important for metabolism, DNA synthesis and growth. For the Central nervous system alkalosis can lead to headaches, drowsyness, tetany convulsions and acidosis can lead to respiratory dysfunction, drowsiness and progressing into a coma.
What is blood pH kept normal by?
Blood pH is kept normal via buffering and excretion. H+ ions can be gained from generation from CO2 (CO2 + H2O becomes H2CO3 via carbonic anhydrase which becomes H+ and bicarbonate), production of nonvolatile acids from metabolism (phosphoric and sulphuric acid, lactic acid and ketone bodies), due to loss of bicarbonate in diarrhea or other non gastric GI fluids or in the urine. Loss can be done via utilisation of H+ in metabolism, loss in vomit or urine and hyperventilation.
How do we remove CO2 from our system? What do changes in ventilation do?
We can remove CO2 via the lungs, for this it needs to be buffered in traansit and we need to keep breathing. It is buffered by haemoglobin, as bicarbonate and a small amount in the blood. With less ventilation (hypoventilation) we get respiratory acidosis due to a higher H+ ion concentraion, with too much ventilation (hyperventilation) we exhale more CO2 and hence get respiratory alkalosis due to lower H+ concentration.
What is done with non volatile acids and their by products?
Metabolism produces non volatile acids, these are buffered via bicarbonate, proteins and phosphate as well as dilution (exchange with bone minerals), this prevents pH falling to dangerous levels. The H+ produced must still be expelled and is done via reactions with bicarbonate (which then has to be replaced).The kidney can reabsorb or excrete more bicarbonate in order to maintain this system.
