Acid Base Balance II Flashcards
Describe hypercapnia
high carbon dioxide
What stimulates central chemoreceptors
hypercapnia, pH
What is the main function of the central chemoreceptors
drive breathing
Who identified that central chemoreceptors are stimulated by pH
Isidore Leusen
Where are central chemoreceptors located
brain parenchyma
What bathes the central chemoreceptors
brain extracellular fluid
Which chemoreceptors are excretely expressed
central
What cell type are central chemoreceptors
neuronal
What is the blood brain barrier NOT permeable to
bicarbonate or hydrogen ions
What is the MAIN stimulation for central chemoreceptors
increased CO2, therefore pH fall
How does the BBB compensate for pH changes
can upregulate its permeability to bicarbonate
Why is brain extracellular fluid capacity to buffer pH low
fewer proteins
What is a drawback of brain extracellular fluid having low buffering capacity
small changes in CO2 will cause large pH changes
What concentrations are affected in metabolic disorders
hydrogen and/or bicarbonate
What is the impact of metabolic disorders compared to respiratory disorders on brain extracellular fluid pH
metabolic disorders change BECF pH by a very small amount compared to respiratory
Where are central chemoreceptors located
ventrolateral medulla and brainstem nuclei
What are the two central chemoreceptor populations
acid activated, acid inhibited
What neurotransmitter is associated with acid activated central chemoreceptors
serotonin
What neurotransmitter is associated with acid inhibited central chemoreceptors
GABA
What can some sudden infant death babies lack
serotonergic neurones
What defect might sudden infant death babies have
defect in central chemoreceptors
What receptors are stimulated during respiratory acidosis
central and peripheral chemoreceptors
Which receptors play the biggest role when oxygen levels are normal
central chemoreceptors
Which receptors have the fastest response during respiratory acidosis
peripheral chemoreceptors
Definition of normoxic
normal oxygen levels
When does metabolic acidosis occur
extreme hyperventilation
Describe carbon dioxide in metabolic acidosis
fall in partial pressure of CO2
What drives the acute response in metabolic acidosis
peripheral chemoreceptors
What is the effect of hyperventilation on pH
pH increases
How does metabolic acidosis affect breathing rate
breathing rate increases
What is the ONLY long term regulation of pH
renal mechanisms
What are the 3 mechanism of the renal system for pH regulation
bicarbonate handling, urine acidification, ammonia synthesis
What does bicarbonate handling mean
bicarbonate is reabsorbed
Where is the majority of bicarbonate reabsorbed
90% in proximal tubule
What enzyme catalyses the break down of carbonic acid
carbonic anhydrase
What does base conservation mean
bicarbonate conservation
What is the main contributer to base conservation
ammonia synthesis
What can generate bicarbonate
renal epithelial cells
What can undergo urine acidification
uric acid, creatinine
Where does urine acidification occur
nearly all the way down the nephron
TRUE or FALSE - ammonia is impermeable across the cell membrane
false - its permeable
What does ammonia come from in renal cells
break down of glutamine
What does ammonium allow the secretion of
hydrogen ions
What does ammonia production prevent
acidification of the urine
What increases during alkalosis
bicarbonate excretion, pH increases
What decreases during alkalosis
plasma pH, H+ excretion
What increases during acidosis
H+ excretion, plasma pH
What stays the same during acidosis
bicarbonate excretion
Describe carbon dioxide levels during respiratory alkalosis
CO2 decreases
When is respiratory acidosis seen
lungs have a problem excreting CO2
What diseases would have a respiratory acidosis
emphysema, chronic bronchitis
When would metabolic acidosis occur
ingestion of acid, loss of alkaline fluid, diarrhoea, cholera
What is stimulated during metabolic acidosis
central chemoreceptors to increase ventilation
In what disorder does the renal system not contribute to
metabolic alkalosis
Where does compensation come from for metabolic alkalosis
respiratory system
What is a mixed disorder
more than one disorder e.g. respiratory and metabolic acidosis
Examples of mixed disorders
Alcoholics, asthma, COPD, salicylate poisoning
Which is the most life threatening mixed disorder
asthma
What mix disorders do COPD patients have
respiratory acidosis and metabolic alkalosis
What mix disorders do patients with salicylate poisoning have
respiratory alkalosis and metabolic acidosis
