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ESA 3 - Urinary > Session 5 - Renal Control Of Plasma Potassium > Flashcards

Session 5 - Renal Control Of Plasma Potassium Flashcards

1
Q

What is the normal range for plasma pH?

A

7.35 - 7.45

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2
Q

Which two organs are the major control centre for the Carbon Dioxide / Hydrogen Carbonate buffer system?

A

The lungs control the Carbon Dioxide concentration

The Kidneys control the Bicarbonate concentration

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3
Q

What is the normal ratio for Hydrogen Carbonate: Carbon Dioxide in plasma?

A

20:1

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4
Q

How is a Respiratory Alkalaemia caused?

A

Hyperventilation leads to Hypocapnia
This increases the ratio of HCO3-:CO2 to > 20:1
More protons are now buffered in the plasma
Hence pH rises

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5
Q

How can the kidneys compensate for Respiratory Acidaemia?

A

If pCo2 rises then pH will fall. The kidneys will compensate for this by reducing excretion of bicarbonate.
More hydrogen ions now buffered so pH rises to normal levels

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6
Q

How does persistent vomiting cause a metabolic alkalosis?

A
  • Protons are vomited out in the stomach acid
  • More hydrogen ions are now needed to be made
  • Production of protons also means more HCO3- are made
  • These are transported straight into the blood
  • More Protons buffered in blood -> pH rises
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7
Q

How is a Metabolic Acidaemia compensated for?

A
  • If HCO3- is low, then CO2 needs to be lowered proportionally
  • This can be done by increased ventilation by the lungs
  • More CO2 removed to pH rises
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8
Q

Why can a Metabolic Alkalosis not be fully compensated for by the lungs?

A

This would require ventilation to fall dramatically depending on the severity of the alkalosis. Ventilation needs to remain relatively high in order to prevent hypoxia

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9
Q

How is HCO3- absorbed in the PCT?

A
  1. Na/K ATPase sets up gradient for Na entry into cells
  2. Protons pumped out of cell in exchange for Na
  3. H+ + HCO3- -> H20 + CO2, CO2 then enters cells
  4. CO2 reacts with H20 to make HCO3-
  5. HCO3- then travels through basolateral membrane + into plasma
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10
Q

By what two substances are Hydrogen ions buffered in the urine?

A

Ammonia and Phosphate

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11
Q

How can persistent vomiting cause hypokalaemia?

A
  • Incraesing conc of HCO3-
  • Body stops actively secreting Protons
  • As proton secretion has stopped in kidneys less potassium is absorbed
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12
Q

What are some of the side effects of hypokalaemia?

A
  • Tetany
  • Parasthesia
  • CVS problems
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13
Q

How may a metabolic acidosis be caused?

A
  • Excess metabolic acids produced
  • Acids are ingested
  • Loss of HCO3-
  • Problem with renal excretion of acid
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14
Q

What is the Anion Gap?

A

The difference between the sum of the measured concentrations of Sodium + Potassium and the sum of measured concentrations of Chloride and Hydrogen Carbonate.

Anion Gap = (Na+ + K+) - (Cl- + HCO3-)

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15
Q

Describe some effects of Acidaemia?

A
  • Decreased enzyme function
  • Decreased cardiac + skeletal muscle contractility
  • Decreased glycolysis rate
  • Decreased hepatic function
  • Increased potassium in plasma
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16
Q

How does aldosterone effect potassium secretion?

A
  • It increases the transcription of the sodium/potassium ATPase
  • also increases transcription of eNaC and K+ channels
  • hence more aldosterone = More potassium secretion
17
Q

What is the relationship between plasma pH and secretion of potassium?

A

Acidaemia = Less potassium in parietal cells = Less secretion

Alkalaemia = More potassium in parietal cells = More secretion

18
Q

How does Insulin effect ICF levels of Potassium?

A
  • Potassium in splanchic blood stimulates insulin release
  • Increase amounts of NA/K ATPases
  • hence potassium conc rises in ICF
19
Q

How does cell lysis effect ICF levels of Potassium?

A

Potassium released from ICF -> ECF

20
Q

How does Aldosterone effect ICF levels of Potassium?

A
  • Increased transcription of Na/K ATPase
  • also increases eNaC and Potassium channels in apical membrane
  • This increases ICF potassium
21
Q

How does exercise effect ICF levels of Potassium?

A
  • Skeletal muscle contraction gives net release or potassium
  • Increased potassium in plasma
  • Less ICF potassium
22
Q

How do Catecholamines effect ICF levels of Potassium?

A
  • Beta 2 agonists stimulate Na/K ATPase

- Hence ICF potassium increases

23
Q

How does Plasma Hyperosmolarity effect ICF levels of Potassium?

A
  • Hyperosmolarity causes water to move into ECF
  • Potassium follows down conc gradient
  • Potassium ICF conc falls
24
Q

Name some causes of Hypokalaemia

A
  • Inadequate intake of potassium
  • Excessive loss (GI or Renal)
  • Alkalosis
25
Q

Name some causes of Hyperkalaemia

A
  • Inadequate renal excretion
  • Kidney Injury
  • Low Mineralocorticoid effect
  • Acidaemia
  • High cell lysis
26
Q

What is th effect of hypokalaemia on the heart?

A
  • Hyperpolarises the RMP
  • More fast Na+ channels now in active form
  • Heart is more excitable

ESA 3 - Urinary (9 decks)

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