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SM Renal > Physiology 7 > Flashcards

Physiology 7 Flashcards

1
Q

pH refers to what

A

free unbound hydrogen ion concentration

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2
Q

what happens if there is an increase in the hydrogen ion concentration

A

A decrease in the pH

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3
Q

What is the pH of the blood

A

between 7.35 and 7.45

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4
Q

venous blood is more or less acidic than arterial blood and why

A

Venous is more acidic due to the presence of CO2 and therefore carbonic acid (weak acid)

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5
Q

What happens if the pH of blood is less than 7.35

A

Patient is suffering from an acidosis

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6
Q

What happens if the pH of blood is more than 7.45

A

Patient is suffereing from an alkalosis

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7
Q

A relatively small change in pH reflects what

A

A larger change in H+ concentration

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8
Q

What are the units of the H+ ion concentration

A

nanomoles per liter (x10 ^9)

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9
Q

What can acidosis lead to

A

Depression of the CNS

disorientated, could die after lapsing into a coma in extreme cases

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10
Q

What can alkalosis lead to

A

Over-excitability of both the peripheral NS and in more severe cases the CNS

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11
Q

What happens if the Sensory fibres are overstimulated

A

Pins and needles

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12
Q

What happens if the Motor fibres are overstimulated

A

Muscle twitches and spasms –> spasms of respiratory muscles in severe cases

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13
Q

What can influence the way in which proteins are folded and what does this result in

A

H+ concentration and pH

Enzymes activity can be altered because of this

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14
Q

What happens in the kidney when a patient becomes acidotic

A

Renal tubular cells increase H+ secretion

There is a corresponding decrease of K+ ion secretion which can lead to K+ ion retention

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15
Q

How is H_ continually added to the plasma

A

Carbonic acid formation
Inorganic addict produced during breakdown of nutrients (lactic acid or free fatty acid)
Organic acids resulting from metabolism

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16
Q

How is carbonic acid formed (HCO3)

A

Water + CO2

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17
Q

Why is the formation of HCO3 not normally a problem

A

Respiratory system can remove this and regulate the levels of this

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18
Q

Why can uncontrolled diabetes mellitus cause an increase of H+ ions

A

the main fuel resource used here is fat metabolism which causes an increase in the production of ketoacids and therefore cause an imbalance of acid-base balance

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19
Q

What is a strong acid

A

An acid which completely dissociates in solution

20
Q

What is a weak acid

A

An acid which partially dissociates in solution

21
Q

What is a buffer system

A

Consists of a pari of substances - once can yield free H_ as the H+ decreases and another that can bind free H+ when H+ concentration increases.

22
Q

If excess H+ ions are added to a weak acid, what does the buffer do

A

It mops up the excess leading to the formation of more of the strong acid

23
Q

If excess base is added to a weak acid, what does the buffer do

A

equilibrium shifts an increase in the dissociation rate occurs

24
Q

What does pK tell us

A

The pH at which the reaction will be at equilibrium

25
Q

What is the formula to calculate the dissociation constant

A

K= [H+] [A-] / [HA]

26
Q

What is the most important buffer system in the body

A

CO2 - HCO3 buffer

27
Q

How can we calculate the pH using the Henderson-Hasselbalch equation

A

pH = pK + log [HCO3-] / [H2CO3]

28
Q

Why is the CO2 - HCO3 buffer so important

A

The pH of the body = kidneys / lungs

29
Q

What do the kidneys regulate

A

The plasma concentration of bicarbonate ions

30
Q

What doe the lungs regulate

A

The levels of the CO2 in the blood

31
Q

How do the kidneys control the concentration of Bicarb

A
  1. Variable reabsorption of filtered HCO3 back into the blood
  2. Kidneys can generate “new” HCO3 to the blood
32
Q

Why is the HCO3 reabsorption important

A

If none was reabsorbed then more H+ ions would be in the blood and we would become acidotic

33
Q

Describe the difference between the H+ conc and the Bicarb ions

A

H+ ions are nano molar range

Bicarb ions are in the mili molar range

34
Q

Where does H+ ion concentration occur

A

Proximal and distal tubules as well as the collecting duct of the nephron

35
Q

Describe the filtration of the bicarb ions

A

They are freely filters but cannot cross the apical membrane of the tubular cells - we need an indirect way of getting the bicarb ions from the tubular fluid back towards the blood

36
Q

How is Bicarb reabsorbed

A

Water and carbon dioxide combine to form carbonic acid (H20 +CO2 –> H2CO3)
The carbonic acid then dissociates inside the epithelial cell to form H+ + HCO3-
The H+ is then filters across the membrane in exchange of a sodium ion into the tubular fluid
Bicarb is then released back into the interstitial fluid along with the Na+ ion

37
Q

What happens if we have CO2 retention

A

we observe an increase in H+ ion secretion by the renal tubular cells

38
Q

What drives bicarbonate ion reabsorption

A

H+ secretion

39
Q

Where is titratable acid broken down

A

it isn’t - it is excreted in the urine

40
Q

What is the next most plentiful buffer in the filtrate when the Bicarb ions are low (due to them being reabsorbed)

A

Phosphate ions

41
Q

What does H+ combine with when phosphate acts as the tubular buffer

A

Acid phosphate which is then excreted in the urine

42
Q

What is titratable acid

A

The amount of H+ excreted as H2PO4- is measured as titratable acid

43
Q

What is the maximum amount of titratable acid that can be excreted in a day

A

40 mmol/day

44
Q

How is ammonia formed in the tubular cells

A

glutamine (from the liver) is broken down by glutaminase to form ammonia

45
Q

How can ammonia diffuse so easily

A

It is a gas

46
Q

What 3 things does H+ ion drive

A

Bicarbonate ion reabsorption
Formation of acid phosphate (titratable acid)
Forms ammonium ion

47
Q

The excretion of TA and NH3 simultaneously rids the body of what
What does this do

A

Acid load

Regenerates the buffer stores (alkalinises the body)

SM Renal (23 decks)

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