22396434
Description
Flashcards by Evian Chai, updated more than 1 year ago
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Created by Evian Chai
over 4 years ago
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| Question | Answer |
| Where are the three locations of renal acid/base handling? | 1. Proximal convoluted tubule 2. Ascending loop of henle 3. Cortical collecting ducts at intercalated cell type A |
| When does H+ excretion occur? | When there is no bicarbonate in the tubular lumen, H+ will combine with a non-bicarbonate buffer and be excreted |
| What is the pH determining acidosis/alkalosis? | 7.35 |
| What is the bicarbonate buffer system? | CO2+H20<->H2CO3<->HCO3-+H+ |
| What is respiratory acidosis caused by? | Insufficient CO2 excretion by lungs aka hypoventilation |
| What is metabolic acidosis caused by? | Fall in plasma HCO3- due to: 1. True HCO3- deficet (renal tubular acidosis/diarrhea) 2. H+ gain from exogenous acid, abnormal carb/lipid/protein metabolism |
| What causes respiratory alkalosis? | Fall in pCO2 due to: 1. Excess central respiratory drive (from aspirin overdose/fever) 2. Hypoxic stimulation (altitude increase, hyperventilation, pulmnary embolism) |
| What causes metabolic alkalosis? pH>7.45 | Increased plasma bicarbonate due to: 1. Loss of gastric acid from vomiting 2. Excess aldosterone (increases H+ ATPase) 3. Excess alkali ingestion |
| What causes acute respiratory acidosis? | 1. Airway obstruction eg. asthma 2. Drug induced eg. narcotics |
| What are the three sources of acid loss? | 1. Utilisation of H+ to metabolise organic anions 2. Vomit/urine 3. Hyperventilation |
| What are the 3 sources of acid gain? | 1. Metabolic acid production from proteins etc. 2. H+ intake from CO2 3. Loss of bicarbonate in urine/diarrhea |
| What 3 types of airway obstriction cause CHRONIC respiratory acidosis? | 1. Lung damage (fibrosis) 2. Chest wall disorders 3. Neuromuscular disorders like lateral scelerosis |
| pH= pK+ log[(...)/(...) CB WA | 1. HCO3- (CB) 2. H2CO3 OR PCO2 |
| Normal Values Body pH= ... Parterial CO2: ... Aterial/venous [HCO3-]= ... Aterial pH= ... | 1. pH=7.35-7.45 2. Parterial CO2=4-6kPa 3. 25nM 4. arterial pH=7.5 |
| How does the respiratory brain stem respond to metabolic acidosis? | Increase ventilation to decrease pCO2, increasing pH |
| How does glutamine metabolism add new HCO3 to the plasma? | 1. Glutamine (filtered) enters tubular epithelial cell 2. Glutamine breaks down into NH4+ + HCO3- 3. HCO3- reabsorbed into interstitial fluid 4. NH4+ goes to tubular lumen via Na+NH4+ cotransporter and is excreted |
| How does filtered HCO3 in the filtrate get reabsorbed? | 1. In the tubular lumen, it combines with H+ to form H2CO3 2. H2CO3--> CO2+H20, enters tubule epithelial cell 3. Reabsorbed (see next slide) |
| How does bicarbonate reabsorption occur in the tubular epithelial cell? | 1. H20+CO3 combines into H2CO3 via enzyme carbonic anhydrase 2. H2CO3-->H+ + HCO3- 3. HCO3- reabsorbed via HCO3/Na+ cotransporter 4. H+ goes to tubular lumen via H+/Na+ exchanger |
| How do the following respond to respiratory alkalosis? 1. Chemical buffers 2. Respiratory brain stem 3. Renal mechanisms | 1. As CO2 concentration falls, plasma HCO3 combines with H+ to form H20+CO2. So, concentration of HCO3-/H+ drops 2. Lower ventilation if possible 3. Lower H+ secretion in tubules, so less to combine with HCO3- for reabsorption (so less HCO3- in plasma). Produces alkaline urine |
| How do the following respond to respiratory acidosis: 1. Chemical buffers 2. Brainstem respiratory centre 3. Renal mechanisms | 1. As more CO2 is present, more HCO3- + H+ is produced via bicarbonate buffer system 2. Cannot be adjusted as ventilation is issue 3. Increase HCO3- reabsorption to increase secretion/excretion of H+ Increase glutamine metabolism to increase HCO3 in plasma Produces acidic urine |
| How do the following respond to metabolic alkalosis: 1. Chemical buffers 2. Respiratory brainstem 3. Renal mechanisms | 1. Fall in H+ pushes rxn left, generating more HCO3- and H+, and decreasing CO2 2. Respiration slows (hypoventilation) to retain more CO2 to make HCO3-/H+ 3. Excess bicarbonate excreted |
| How do renal mechanisms respond to metabolic acidosis? | 1. Increase H+ secretion 2. Increase glutamine metabolism Both these raise plasma HCO3 to a normal level |
| How do chemical buffers respond to metabolic acidosis? | 1. Rise in H+ will cause HCO3- to drop as it combines to form CO2. pCO2 will rise |
| Chemical buffers work in {{c1::seconds}} eg. ... in ECF,...in ICF, ...in urine Brain respiratory center works in {{c5::minutes}} in response to changes in arterial changes Works by...to expel/retain CO2 Renal mechanisms work in ... For each H+ secreted, HCO3- is added to blood | 1. Seconds 2. Bicarbonate, phosphate, phosphate/ammonia 1. Minutes 2. pCO2/pO2 3. Adjusting ventilation 1. Hours to days |
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