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Y2 - Urinary > Lecture 10 - Acid/Base Balance In The Kidney > Flashcards

Lecture 10 - Acid/Base Balance In The Kidney Flashcards

1
Q

What happens if the plasma pH is not maintained within a tight range?

A

Proteins/enzymes denature

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2
Q

What is the healthy pH range of the blood plasma?

A

7.35 - 7.45

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3
Q

What is the pH range that the urine varies between?

A

4.5 - 8.5

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4
Q

How does Alkalemia affect plasma free calcium levels?

A

Decreases free levels of calcium

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5
Q

Describe the mechanism by which alkalosis causes lower free calcium levels:

A

When the blood is alkalotic the hydroxyl group of albumin dissociates its H+, this makes more Ca2- bind to albumin

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6
Q

What plasma protein is the main plasma protein in the blood?

A

Albumin

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7
Q

Describe the mechanism by which alkalosis causes lower free calcium levels:

A

When blood is alkalotic the hydroxyl group on the albumin dissociates releasing H+ to try and decrease blood pH

This change on the albumin leads to Ca2+ binding to t he albumin making it no longer free decreasing plasma Ca2+ levels

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8
Q

So if alkalosis causes decreased free plasma Ca2+, how does this affect nerves?

A

Increased neuronal excitability ( so action potentials fired at slightest signal)

Sensory changes like numbness/tingling with muscle twitches

Can lead to sustained contractions/paralysis

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9
Q

How does acidosis change free calcium levels in the plasma?

A

Increases free calcium levels in the plasma

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10
Q

Describe the mechanism by which acidosis causes higher free calcium levels:

A

When the blood is acidotic the H+ binds to the O- of the what once was the hydroxyl group on the albumin

This leads to Ca2+ being released from the album in and less Ca2+ binding to the albumin
So plasma levels of free Ca2+ increases

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11
Q

What affect does increased free plasma Ca2+ have on other ion levels and why is this dangerous?

A

Increases plasma [K+] levels

Leads to cardiac excitability being affect leading to Arrythmias

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12
Q

What are the 2 sources of H+ in the body?

A

Diet

Metabolism

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13
Q

What are some examples of how acids can be obtained?

A

Proteins = amino acids
Lipids = fatty acids
Carbs = lactic acids

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14
Q

What are the 3 different buffer systems to buffer the H+ in the body?

A

HCO3– in blood/ECF

Proteins, Hb and Phosphates in cells

Phosphates and ammonia in urine

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15
Q

What are the 2 organs/systems that regulate plasma pH?

A

Lungs/respiratory

Kidneys/renal system

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16
Q

What is the relative speed by which the ventilation system and the renal system can compensate for plasma pH levels?

A

Lungs/ventilation = rapid response

Kidneys/renal = slower

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17
Q

How do the lungs help regulate blood pH?

A

Changing ventilation rate changes levels of CO2 present in the blood

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18
Q

How do the kidneys alter blood pH?

A

Excreting and reabsorbing H+

Changing rate at which HCO3- is reabsorbed pr excreted in the urine

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19
Q

How much of the HCO3- does the body try and reabsorb from the filtrate in the PCT?

A

All of it

20
Q

What form is HCO3- absorbed from the filtrate into the PCT cell as?

A

CO2 + H20

HCO3- + H+ = H2CO3
H2CO3 becomes CO2 + H2O with help of Carbonic anhydrase

21
Q

Describe how HCO3- is reabsorbed into the blood from filtrate:

A

Na+/K+ ATPase on basolateral membrane pumps Na+ into blood establishing Na+ gradient

Carbonic acid broken down to CO2 + H2O by carbonic anhydrase
CO2 and H2O diffuses into the cell

CO2 + H2O remade into H+ + HCO3- in cell with help from C.A

HCO3- symported into blood across basolateral membrane with Na+

H+ in the cell antiported into blood across apical membrane and Na+ brought into cell

22
Q

What are the 2 buffer systems present in the plasma that help prevent blood being too acidic?

A

Phosphate buffer

Ammonia (NH3) buffer

23
Q

How does the phosphate buffer system in the urine act to prevent blood becoming to acidic?

A

H+ reacts with HPO4(2-) forming H2PO4(-)

H2PO4(-) can then be excreted in the urine

24
Q

How does the ammonia buffer system in the urine act to prevent plasma pH becoming to acidic?

A

NH3 + H+ forming NH4+

This is now charged (ammonium) preventing it entering into any cells which constricts it to the lumen ensuring it is excreted

25
Q

What is the process by which the PCT cells can produce HCO3- to prevent blood becoming too acidic?

A

Cell makes glutamine

Glutamine converted to alpha ketoglutarate and 2NH4+

Alpha ketoglutarate converted to 2HCO3- to be reabsorbed into blood

Ammonium (2NH4+) broken down into ammonia (2NH3) and 2H+
2NH3 then diffuses back into lumen to join monitor buffer system
H+ then removed back into lumen

26
Q

What are the cells that deal with acidosis in the DCT/CD?

A

Alpha intercalated disc cells

27
Q

What are the cells that deal with alkalosis in the DCT/CD?

A

B intercalated cells

28
Q

What ion can be heavily influenced by the pH/ being acidotic or alkalotic?

Why is this dangerous?

A

Potassium levels
Hyperkalaemia and hypokalaemia

Can lead to cardiac arrhythmias

29
Q

How can acidosis affect potassium levels in the blood and explain why?

A

Hyperkalaemia
High H+ in plasma exchanged with K+, H+ moved into cell and K+ into the blood from the cell

30
Q

How can alkalosis affect potassium levels in the blood and explain why?

A

Hypokalaemia
Since H+ levels in blood low
H+ moved from inside of cells into blood and therefore K+ moved from blood into cells

31
Q

What is the main cause of respiratory alkalosis?

A

Hyperventilation

Lots of CO2 breathed out (hypocapnic) so less carbonic acid

32
Q

What is the form of compensation that occurs with respiratory alkalosis?

A

Renal/metabolic compensation

Less HCO3- reabsorbed in PCT

HCO3- secreted in DCT/CD
H+ reabsorbed with K+

33
Q

What is the most common cause of Respiratory acidosis?

A

Hypoventilation

More CO2 retained so (Hypercapnic) so higher levels of Carbonic acid

34
Q

What is the form of compensation that occurs with respiratory acidosis?

A

Renal/metabolic compensation

More HCO3- reabsorbed in kidneys and H+ secreted

35
Q

What can cause Metabolic alkalosis?

A

Excess vomiting of acidic stomach contents

Ingesting excess HCO3- like through antacids

36
Q

What are the compensatory mechanisms for a Metabolic Alkalosis?

A

Resp compensation = Hypoventilation (more CO2 retained to make more acidic blood)

The hypoventilation leads to more HCO3- being made from the extra CO2 so some RENAL compensation occurs so less HCO3- reabsorbed in PCT

37
Q

What can cause metabolic acidosis?

A

Dietary and metabolic input of H+ exceeds excretion

Or losing to much HCO3- (diarrhoea)

E.g:
Lactic acidosis
Ketoacidosis

38
Q

What compensation occurs with metabolic acidosis?

A

Respiratory compensation = hyperventilation to increase removal of CO2

Renal compensation = inc reabsorption of HCO3- and DCT/CD secretion of H+

39
Q

Look at the last slide, look at 1. Investigations and describe what type of acid base disturbance has occured:

A

Metabolic acidosis with respiratory compensation (partial)

PH low
PCO2 low so not the cause of the acidosis but HCO3- is low so its the cause

40
Q

Look at the last slide, look at 1. Investigations and describe what type of acid base disturbance has occured:

A

Metabolic acidosis with respiratory compensation (partial)

PH low
PCO2 low so not the cause of the acidosis but HCO3- is low so its the cause

41
Q

What is the anion gap?

A

The difference between measured cations and anions

42
Q

How do you determine the anion gap?

A

([Na+] + [K+]) - ([Cl- + [HCO3-])

Basically sum of major cations - sum of major anions

43
Q

What form of acidosis is the anion gap remaining unchanged?
Why?

A

Metabolic acidosis

Not enough HCO3- but is replaced by Cl-

44
Q

What are some of the common causes of hypokalaemia?

A

Alkalosis

GI loses

Renal loses

45
Q

What are some examples of renal loses that can cause hypokalaemia?

A

Diuretics like furosemide

Too much aldosterone production/over activation of RAAS

Renal tubular acidosis

Y2 - Urinary (24 decks)

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