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Renal > 2.2: Physiology 7 > Flashcards

2.2: Physiology 7 Flashcards

1
Q

What is the average pH of blood?

A

7.4

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2
Q

A small change in pH reflects:

  • Large
  • Small

change in [H+]?

A

A small change in pH represents a LARGE change in H+

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3
Q

What is the affect on pH of increasing [H+]?

A

Increasing [H+] causes decreased pH (more acidic)

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4
Q

What is the equation for pH?

A
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5
Q

Describe the affect of acidosis and alkalosis on the CNS?

A

Acidosis can depress the CNS

Alkalosis causes overexcitation of the PNS and then CNS

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6
Q

Fluctations in [H+] alter nerve activity, enzyme activity and K+ activity.

True or false?

A

True

Fluctations in [H+] alter nerve activity, enzyme activity and K+ activity

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7
Q

H+ is continually added to the body as a result of…?

What are the three sources?

A

H+ is continually added to the body as a result of metabolic activity

  • Carbonic Acid Formation
  • Inorganic acid produced during the breakdown of nutrients
  • Organic Acids resulting from metabolism
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8
Q

Describe the dissocation of:

  • Strong acids
  • Weak acids

in solution?

A

Strong acids fully dissociate in solution

Weak acids partially dissociation in solution

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9
Q

Describe a buffer solution?

A

This consists of two substances:

  • Once can yield free H+ when [H+] decreases
  • One can bind free H+ when [H+] increases

It can resist changes to pH when small amounts of acid or alkali are added

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10
Q

Describe what happens if acid (H+) is added to this system?

  • What happens to equilibrium?
  • What happens to HA?
  • What happens to A-?
A

Equilibrium shifts to the left

[HA] rises

[A-] falls

The rise in H+ has been BUFFERED by producing more HA

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11
Q

Describe what happens if base (A-) is added to this system?

  • What happens to equilibrium?
  • What happens to HA?
  • What happens to A-?

What happens to H+?

A

BODY MOVES EQUILIBRIUM TO THE RIGHT TO PREVENT ALKALOSIS

Equilibrium shifts to right

HA falls as more dissociates

A- increases as H+ is being used up

H+ is used up (decreases)

Dissociation of more HA buffers a rise in pH due to less H+

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12
Q

What is the dissociation constant?

A

Right over left

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13
Q

What is pK?

A

Pk = - log K

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14
Q

What is the henderson hasselbach equation?

A
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15
Q

What is the most important physiological buffer?

A

The CO2-HCO3 Buffer

(Carbon Dioxide Bicarbonate Buffer)

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16
Q

How is carbonic acid formed?

Catalyst?

A

H2C03 is formed from CO2 and H20

Carbonic acid is formed from carbon dioxide and water

Catalyst is carbonic annhydrase

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17
Q

Why is the carbon dioxide bicarbonate system so important?

A

HCO3 is controlled by the kidneys

pCO2 is controlled by the lungs

These set the pH of the WHOLE body

at 7.4

18
Q

What is the first line of defence to changes in the acid-base balance?

A

The Buffer System

19
Q

What does pK actually tell us?

A

It tells us the pH at which the reaction will be at equilibrium

20
Q

Describe the role of the kidneys in regulation of HCo3-?

A
  • Variable reabsorption of filtered HCo3-
  • Kidneys can add ‘new’ HCO3 to the blood

(HCO3 in renal vein > than in renal artery)

Both depend on H+ secretion into the tubule

21
Q

How much HCO3- is filtered per day?

How much is reabsorbed?

What would happen if this amount wasn’t reabsorbed?

A

4320mmol/day is filtered

Normal kidneys are able to reabsorb all of this

If it wasn’t absorb, this would upset the acid base balance (equivalent to to adding lots of acid to the body)

22
Q

How is HCO3- reabsorbed?

A

Cannot be moved freely across membrane

Binds with hydrogen to become carbonic acid

Becomes CO2 and water

Passively crosses membrane

23
Q

H+ ion secretion drives the indirect flow of bicarbonate ions (reabsorption)

True or false?

A

True

24
Q

H ion secretion drives …?

H ion secretion is driven by?

H ion secretion comes from?

*IN THE CONTEXT OF BICARBONATE REABSORPTION*

A

H ion secretion drives indirect flow of bicarbonate ions

H ion secretion is driven by partial pressure of Co2

H+ ions secreted from tubular cells

25
Q

What happens to H ion secretion if Co2 is retained?

A

Co2 retention leads to increased H ion secretion by the tubular cells

26
Q

As well as retaining filtered HCo3, what else can the kidneys do?

Explain this mechanism?

A

Kidneys can also produce new HCO3-

When concentration of bicarbonate in the tubular fluid is low, H+ binds to PHOSPHATE

Forms Phosphoric Acid

27
Q

Describe the affect forming phosphoric acid has on bicarbonate?

A

Formation of phosphoric acid invovles a H+ ion being added to phosphate

H+ secretion comes from carbonic acid being converted into bicarbonate

The H+ combines wirth phosphate to make phosphoric acid

This produces bicarbonate which is reabsorbed

Phosphoric acid formation increases plasma bicarbonate levels

–> NEW BICARBONATE

28
Q

How is ‘new’ bicarbonate formed?

A

Carbonic acid breaks down to release a H+

This H+ bonds with phosphate to make phosphoric acid which is secreted

The carbonic acid forms bicarbonate

This passes into interstitial fluid and then plasma

29
Q

What is the phosphoric (H2PO4) acid also called?

A

Titratable acid

30
Q

For every H+ ion that is secreted as titratable acid, how many bicarbonate ions are added to blood?

A

For every ONE H+ ion, ONE bicarbonate ion is added to blood

31
Q

What else can be used as a buffer except bicarbonate and phosphate?

When would this occur?

A

Ammonia

In severe acidosis when all the phosphate has been used up

32
Q

Describe formation of ammonia?

A

Glutamine from liver is broken down by glutaminase

The end product NH3 binds with H+ to form NH4 (Ammonium ion)

This is excreted

33
Q

When ammonia is used as a buffer:

  • What is excreted?
  • What is gain?
A

Ammonia is excreted

Bicarbonate is gained

34
Q

When ammonia is used as a buffer, how many ions of bicarbonate are produced for every ammonium ion secreted?

A

For every ONE ammonium secreted there is ONE bicarbonate added to the blood

35
Q

Measuring the titratable acid measures …?

Measuring the titratable acid does not measure..?

A

Measuring titratable acid measures phosphoric acid

Measuring titratable acid does not measure ammonia

36
Q

True or False?

  • Ammonium ions are normally excreted.
  • Measuring titratable acid measures ammonium ion concentration.
A

FALSE - Ammonium ions are not normally excreted. Only seen after 2-3days of acidosis

FALSE: Measuring titratable acid only measures phosphoric acid concentration. A separate ammonium ion determination is needed

37
Q

H+ secretion by the tubule does three things.

Name them?

A

HCO3- reabsorption

Forms acid phosphate (excretes it as titratable urine)

Forms ammonium ion

38
Q

What is the total H+ secretion in the tubule daily?

What is the amount of H+ excreted daily (in urine?)

THEREFORE, how much new bicarbonate made per day?

A

4360mmol/day

60mmol/day

60 mmol/day

39
Q

The vast majority of H+ is used for..?

A

Bicarbonate Reabsorption

(To prevent acidosis)

40
Q

Excretion of XXX and YYY simulataneously rids the body of acid load and regenerates buffer store.

Name X and Y?

A

Titratable acid (acid phosphate)

Ammonium Ion

Renal (34 decks)

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