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R - Renal physiology (Megan) > Physiology 7 > Flashcards

Physiology 7 Flashcards

1
Q

What is the normal pH and range?

A 
pH = 7.4
range = 7.37 - 7.43
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2
Q

What should the ratio between bicarbonate and carbonic acid be?

A

20:1

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3
Q

What is unique about the bicarbonate buffer system?

A

It is an open buffer system, it includes gas which means the gas can be breathed off, meaning the equation won’t start pushing backwards.

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4
Q

How do we control carbon dioxide?

A

Via the respiratory system

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5
Q

How do we control bicarbonate?

A

Via the kidneys

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6
Q

what is the bicarbonate buffer system equation?

A

carbon dioxide + water = carbonic acid = Bicarbonate + H+ (proton)

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7
Q

How is the pH maintained in the extracellular fluid?

A

Via the bicarbonate buffer mainly

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8
Q

How is the pH maintained in the intracellular fluid?

A

Via importing H+ into cells (so its not free to contribute to pH) - this is done by swapping H+ for a K+ inside the cell, or by adding Cl- alongside H+.

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9
Q

What is a complication of acidosis?

A

hyperkalaemia - H+ is swapped for K+ which is now free in the plasma. Hyperkalaemia >5.5 and causes reduction in the resting membrane potential

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10
Q

What is the normal value of Bicarbonate?

A

24mmoles (22-26)

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11
Q

What is the normal value of PCO2?

A

40mmHg

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12
Q

What is a side effect of chronic renal failure?

A

Chronic acid load - the kidneys can’t remove the H+ so bicarbonate is increased by taking it from the bone.

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13
Q

When is intracellular buffering used?

A

In chronic acid loading.

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14
Q

When is the buffer system used?

A

the buffer system is used first to control pH levels, but it doesn’t REMOVE H+.

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15
Q

How do we remove H+ ions?

A

This is done using the kidneys. it is the definitive way to correct pH and occurs after buffering.

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16
Q

What is the point in buffering?

A

It maintains the pH until the kidney fixes it.

17
Q

how is metabolic acid buffered?

A

43% in the ECF, 57% in the ICF.

18
Q

How is respiratory acid buffered?

A

97% in cells (using haemoglobin)

3% in the plasma.

19
Q

What controls bicarbonate?

A

The kidneys

20
Q

What controls carbon dioxide?

A

The lungs

21
Q

How does the kidneys reabsorb filtered bicarbonate?

A

Bicarbonate is filtered at the glomerulus and is in the tubule.

  • hydrogen is transported out of the cell, sodium is transported into the cell to maintain the electrochemical gradient
  • the hydrogen binds with the bicarbonate to create carbonic acid (via carbonic anhydrase)
  • The carbonic acid dissociate into carbon dioxide and water
  • the carbon dioxide is transported into the tubule cell where it binds with water again
  • it creates carbonic acid - which dissolves into H+ and bicarbonate
  • the H+ is secreted (to be reused again) and the bicarbonate is taken up into the blood
22
Q

How does the kidney remove H+ and create new bicarbonate (initially)?

A
  • using diphosphate
  • carbon dioxide from the blood enters the tubule cell, it binds with water and uses carbonic anhydrase to become carbonic acid - it dissociates into bicarbonate (which is reabsorbed into the blood) and into H+ which is excreted into the tubule to be excreted
  • diphosphate is in the tubule lumen - the sodium is absorbed into the tubule cell and Hydrogen is put out to maintain the electrochemical gradient
  • the dibasic phosphate is excreted in the urine
23
Q

Why can H+ not be removed on its own?

A

It would make the urine too acidic

24
Q

What is the pH of the urine?

A

4.5-5.5 (Max 8)

25
Q

How does the kidney excrete H+ and create bicarbonate (long term)?

A

The kidney takes 4-5 days to create glutamine

  • carbon dioxide goes from the blood into the tubule cells, it binds with water and uses carbonic anhydrase to create carbonic acid - this dissociates into H+ and bicarbonate (which is reabsorbed in the blood), the H+ is used in the next step
  • glutamine is broken down in the tubule cell into ammonia (NH3) and glutamate
  • the NH3 is lipid soluble so it goes out into the tubule, it binds with a H+ to create NH4
  • ammonium is insoluble so cannot cross back over the cell membrane - it is excreted in the urine
26
Q

What does carbonic anhydrase do?

A

it is the enzyme in the reaction of building up and breaking down - carbonic acid into carbon dioxide and water - and vice versa

27
Q

What does glutaminase do?

A

It converts glutamine into glutamate and ammonia

28
Q

how is ammonia changed into ammonium in the distal tubule?

A

in the tubule lumen

29
Q

How is ammonia changed into ammonium in the proximal tubule?

A

Inside the tubule cell (ammonium is insoluble so an ammonium transporter is needed to move it out into the tubule lumen) to be excreted

R - Renal physiology (Megan) (8 decks)

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