Urinary System 7 - Acid base regulation Flashcards Preview

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Flashcards in Urinary System 7 - Acid base regulation Deck (20)
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1
Q

List the possible metabolic changes that can cause acidosis or alkalosis

A
  • Acidosis can be caused by H+ gain and HCO3- loss

- Alkalosis can be caused by H+ loss and HCO3 gain

2
Q

What is the normal plasma proton concentration?

A
  • 49nmol/L
3
Q

What is the normal arterial bicarbonate?

A

22-26mEg/l

4
Q

Compare the range for normal blood pH to the range for normal urine pH

A
  • Normal blood pH ranges between 7.35-7.45

- Normal urine pH regulates between 5-8, as it is a regulator

5
Q

Describe the absorption of bicarbonate throughout the kidney

A
  • 80% reabsorbed PCT
  • 10% reabsorbed ascending loop of henle
  • 6% reabsorped DCT
  • 4% reabsorbed collecting duct
6
Q

Why is bicarbonate important?

A
  • It is a high capacity chemical buffer that can respond to changes in metabolic acid and be produced from respiratory acid
7
Q

Write the henderson hasslebach equation with normal values substituted

A

pH=pK + log10(HCO3-/CO2)
pH = 6.1 + log10(24/1.2)
pH = 7.4

8
Q

What is the davenport diagram?

A
  • A graphical respresentation of the association between pH, bicarbonate and carbon dioxide in the blood
  • Plasma bicarbonate on the y axis, pH and [H=] on the x axis, and pCO2 on a bent axis in the right hand corner
9
Q

Explain what the deviations mean on the davenport diagram

A
  • Slight increase in plasma bicarbonate and low pH is due to acute respiratory acidosis
  • Slight decrease in plasma bicarbonate and high pH due to acute respiratory alkalosis
  • Metabolic acidosis recongised by low bicarbonate, low pH
  • Metbolic alkalosis low pH and high bicarbonate
  • Chronic respiratory acidosis is similar to acute but with very high plasma bicarbonate and a more normal pH
  • Chronic respiratory alkalosis is slightly high pH and very low base excess
10
Q

Describe the process of bicarbonate reabsorption in the PCT

A
  • Carbonic anhydrase converts bicarbonate to H2O and CO2. CO2 moves into the cell and is converted back to bicarbonate ions and protons
  • Protons diffuse into filtrate via a H+ ATPase and the sodium proton exchanger
  • Bicarbonate diffuses into the blood through the chloride bicarbonate exchanger, and bicarbonate sodium exchanger (3bicarb to 1Na)
  • Chloride also diffuses into the blood through its channels
11
Q

What are the two types of intercalating cells and what are their functions?

A
  • Alpha cells (acid-secreting)

- Beta cells (bicarbonate secreting)

12
Q

Describe the process in alpha intercalating cells

A
  • Bicarbonate remade in the cytoplasm via CA
  • Protons pumped into tubular fluid via hydrogen potassium ATPase and sodium proton antiporter
  • Bicarbonate diffuses into blood via chloride bicarbonate exchanger, and chloride via channels
13
Q

Describe the process in beta intersticalating cells

A
  • In the cytoplasm, CO2 and H2O used to make bicarbonate and protons
  • Protons pumped into the blood (H+ ATPase, H+/Na+ antiporter and H+/K+ ATPase)
  • Bicarbonate enters the tubular fluid via chloride bicarbonate exchanger, and chloride diffuses back into tubular fluid via its channels
14
Q

Describe the process of HCO3- generation by cells

A
  • Glutamate enters the cell through SGLT-1
  • Glutamate converted to NH4+ and HCO3-
  • HCO3- enters blood (HCO3/CL- exchanger, HCO3/Na+ cotransporter, Na+/K+ ATPase)
  • Ammonium leaves the cell through a NH4/Na+ antiporter to enter the filtrate
  • Can also be produced using carbonic anhydrase and H2O/CO2
15
Q

What is the compensatory mechanism for respiratory acidosis?

A
  • Decrease acid increase bicarbonate

- Intracellular buffering, bicarbonate generation and ammonium excretion

16
Q

What is the compensatory mechanism for respiratory alkalosis?

A
  • Intracellular buffering

- Decreased bicarbonate reabsorption and decreased ammonium excretion

17
Q

What is the compensatory mechanism for metabolic alkalosis?

A

Hyperventillation

18
Q

What is the compensatory mechanism for metabolic acidosis?

A

Hypoventilation

19
Q

What is the blood pH compatable for life?

A

6.8-8 - critically ill

20
Q

What is the normal venous bicarbonate?

A

22-29mmol/L