block 2 lecture 7 acid and base balance Flashcards
what is pH?
hydrogen ion concentration
what is stomach acid pH?
2
what is the pH of extracellular fluid?
7.4
what is the pH of blood?
7.35-7.45
what is the pH of blood to sustain life?
6.8-8
what is it called if we have a blood pH of below 7.35?
acidosis
what is it called if we have a blood pH of above 7.45?
alkalosis
at the pH of 7.4 what is the ratio of bicarbonate ions to pCO2?
20:1
what happens in the bicarbonate buffer system?
hydrogen ions and bicarbonate ions can be converted into carbonic acid which can dissociate into hydrogen ions and bicarbonate ions
the body has 3 buffering systems?
blood buffering system, respiratory system and renal mechanisms
what are the buffering systems in the blood?
bicarbonate buffer, phosphate system and protein buffer system
what is the buffering system in the respiratory system?
removal of CO2 by ventilation
what is the buffering system in the renal system?
excretion of hydrogen ions and reabsorption of bicarbonate ions
what is the carbon dioxide concentration regulated by?
lungs
what is the bicarbonate ion concentration regulated by?
kidneys
what does bicarbonate ion convert a strong acid into?
weak acid
what converts strong base into a weak base?
carbonic acid
what are the two salts of the phosphate system?
sodium dihydrogen phosphate and disodium dihydrogen phosphate
what is the alkaline phosphate salt?
disodium dihydrogen phosphate
what is the acidic phosphate salt?
sodium dihydrogen phosphate
where is the protein buffer system present?
plasma and blood
in the plasma what forms weak acids? (protein buffer system)
carboxylate group and side chains
in the erythrocyte what is the buffer?
haemoglobin
when does the amino group release hydrogen? (protein buffer system)
in the presence of excess base
what accepts a hydrogen atom in the presence of excess acid? (protein buffer system)
carboxyl group
what is important about hemoglobin in the protein buffer system?
Deoxygenated haemoglobin has a high capacity to bind to hydrogen ions which is then released when oxygen enters the capillaries. Haemoglobin prevents the fall in pH when more carbon dioxide enters the capillaries.
what happens to carbon dioxide in the lungs?
bicarbonate ions and hydrogen ions in the blood form carbonic acid which dissociates into water and carbon dioxide which is then removed by ventilation
what happens when metabolic activity increases to pH?
this increases the carbon dioxide concentration ad so the hydrogen ion concentration causing pH to fall
what does increased metabolic activity do to ventilation?
lowers pH which is detected by chemoreceptors which stimulate pulmonary ventilation
what do the kidneys do in the renal system of buffering in short?
excrete hydrogen ions and reabsorb bicarbonate ions
where does bicarbonate reabsorption occur?
proximal convoluted tubule and distal convoluted trubule
where does most bicarbonate reabsorption occur?
proximal convoluted tubule
what does bicarbonate ions combine with to form carbonic acid? (renal system)
hydrogen ions
what dissociates carbonic acid? (renal system)
carbonic anhydrase
where do you find carbonic anhydrase? (renal system)
brush border membrane
what does carbonic anhydrase dissociate into? (renal system)
carbon dioxide and water
where does the carbon dioxide from dissociated carbonic acid go? (renal system)
it diffuses across the apical membrane and the tubular cell
what happens to the carbon dioxide in the tubular cell? (renal system)
combines with water and forms carbonic acid
what happens to the carbonic acid in the tubular cell? (renal system)
rapidly dissociates into bicarbonate ions and hydrogen ions
what is on the apical membrane to remove hydrogen ions?
hydrogen ATPase
where do the hydrogen ions go from the hydrogen ATPase? (renal system)
lumen tubule filtrate
what happens to the bicarbonate and sodium ions from the tubular cell? (renal system)
pumped across the intracellular space into peritubular capillaries
how much reabsorption does the DCT do? (renal system)
10%
what does the DCT do? (renal system)
brings about the removal of acid
why does the pH fall in the collecting ducts?
the distal nephron is impermeable to hydrogen ions as there
what are the mechanisms which try to restore the acid base balance celled?
compensation
what are the two compensatory mechanisms called?
respiratory and renal
which compensatory system is fast?
respiratory
what does respiratory acidosis result from?
accumulation of carbon dioxide due to a failure of pulmonary ventilation
what does metabolic acidosis result from?
accumulating non-volatile acid
what can respiratory acidosis be caused by?
airway obstruction, COPD, asthma, CNS lesion, anasthesia
what can metabolic acidosis be caused by?
formation of acidic ketone bodies, lactic acid build up, reduced ability to excrete acid, diabetes
what is respiratory alkalosis?
increase in pH and decrease in blood pCO2, sustained hyperventilation
what can cause sustained hyperventilation in respiratory alkalosis?
anxious, hypoxia, high altitude, fever, brain stem damage - pons
what can cause metabolic alkalosis?
vomiting, taking antacids
what is the other buffer of the renal system?
ammonia
what catalyses the production of ammonia?
glutaminase
where do you find glutaminase?
PCT
what is ammonia produced from?
ammonia rich amino acids
how does ammonia help remove hydrogen ions?
ammonia comebines with hydrogen ions forming the ammonium ion which is removed by a carrier protein
