Acid Base Balance Flashcards
What is the normal pH of cells?
Between 7.35 and 7.45
What are some of the possible effects of alkalemia?
Lowers the free calcium by lowering the Ca2+ soluability, and causing the ions to com out of solution and the resulting hypocalemia makes the nerves more excitbale, and therefore can produce parastheisa and tetany
What are some of the potential negative effects of acidemia?
Affects the enzyme funciton in many tissues, potassium movement outside the tissues, and therefore effects the excitability, paticularly of the cardiac muscle, and also distrubs enzymes affectin the muscle contractility, glyocolyss and hepatic function
What is the henderson hesslebach equation?
PH= pK + ((HCO3-)/pCo2x 0.23)
What is the significance of the henderson hesslebach equqation?
The ph of blood depends on the raito between HCO3- and Co2
What are the effects of hypoventiliation?
It causes hypocapnia, which then causes a fall in plasma pH and then causes respiratory acidemia
What are the effects of hyperventiliation?
It causes hypoapnia, and the pH increases and therefore causes respiraotory acidemia
What is the role of chemoreceptors in controlling the plasma pH?
Central chemoreceptors change the ventiliation rate due to the respiratory disturbances, and the perihral chemoreceptors detect changes in both pH and Hco3- and alter the respiratory rate as well, but have less of an effect
How do the kidneys help to compensate for respiraotry changes in pH?
Respiratory acidmeia is compensated by the kidneys increasing HCo3 whereas the respiratory alakalemia is compensated by the kidney decreasing the amount of HCO3-
What are metabolic alklalis?
If the plasma HCO3- rises, eg after reapated vomiting (the stomach produced H+ and HCO3- together) the plasma pH will rise
How can the kidneys compensate for metabolic changes in HCO3-?
They can vary the excretion of Hco3- or make more HCO3-
How is HCO3- recovered in the PCT?
Driven by the Na gradient that is established by Na-K-Atpase, Na= movemnt into the cell drives the H+ movemtn out of the cell using the NHE-3 exchanger, and this reacts with HCO3- in the lumen to form CO2, which moves into the cells and recats with water to produce more HCO3-, and HCO3- moves across the basolateral membarne into the ECF via the Na-3HCO3- co transporter
How is HCO3- recovered in the distal nephron?
H+ is pumped across the membrane by a HCO3- pump, as the gradient is not high enough to drive the HCO3- out there is little HCO3- so little Co2 enters the clel, most of the excerted H+ reacts wiht the buffers and remains in the urine HPO4 and HN3+
How is HCO3- produced in the PCT?
The reaction of Glutamine to a- ketoglurate produces HCO3- and ammonium, and HCO3- enter the ECHf and the NH4+ enters the lumen
How is HCO3- created within the distal tubule?
Metabolci activity within the cells produce CO2, reacts with water to produced HCO3- and need to secrete the H+ and buffer them to keep producing the HCO3-
What are the buffers for acid in the urine?
Ammonium and phosphate
What is the cellular response to acidosis in the kidneys?
Enhances he activit of the Na/h exchanger, enhances the production of ammonium in the proximal tubule, and enhances the activity of the proton pump in the distal tubule
What causes the fomration of the anion gap?
Metabollically produced acids such as lactatic acid, have an acsoicated aninon wiht the H+, this reacts with HCO3- to form CO2, and therefore the HCO3- is replaced by another anion and forms the anion gap
What is the anion gap?
Calculated as the difference between (na+) (K+) and (cl-) (Hco3), is normally less due to the presence of other anions but increases if the anions from metabolic acids produce HCO3
How can you correct metabolic alaklosis after persistant vomiting?
HCO3- can be excreted very rapidly following an infusion of HCOS3-
When are the main problems in metabolic alkalsosis?
If there is also volume depletion, and the capcity to lose HCO3- s reduced because of the high rate of HCO3- recovery, as recovering Na+ favours H+ excerttion ad HCO3- recovery
