12: Physiology 8 Flashcards

1
Q

What is the normal pH of the blood?

A

7.4

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2
Q

Which blood vessels have a lower pH?

A

Veins

more CO2

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3
Q

What is the normal blood concentration of bicarbonate ions?

A

22 - 28

sits around 25

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4
Q

What is the normal partial pressure of CO2 in the blood?

A

40 mmHg

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5
Q

What needs to be brought back to normal to

a) compensate for
b) correct

an acid-base imbalance?

A

a) pH

b) pH, [HCO3-], pCO2

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6
Q

What are compensation and correction of an acid-base disturbance?

A

Compensation - bringing pH back to normal

Correction - bringing pH, [HCO3-] and pCO2

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7
Q

What are the four types of acid-base imbalance?

A

Metabolic acidosis and alkalosis

Respiratory acidosis and alkalosis

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8
Q

What solutions are responsible for correcting short-term changes in pH?

A

Buffers

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9
Q

What component of blood acts as a buffer?

A

Hb

unoxygenated blood has a higher affinity for H+ than oxygenated blood

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10
Q

What happens when buffers run out?

A

Kidney replaces them

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11
Q

ph = pk + log(kidneys/lungs)

A
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12
Q

Which organs regulate blood concentration of

a) CO2
b) bicarbonate?

A

a) Lungs

b) Kidneys

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13
Q

What are the normal ranges of concs. for

a) pH
b) bicarbonate?

A

a) 7.35 - 7.45 (normal is 7.4)

b) 22 - 28 (normal is 25)

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14
Q

What general group of diseases causes CO2 retention?

A

Respiratory disease

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15
Q

CO2 retention causes an (increase / decrease) in the concentrations of which ions?

A

H+ (importantly)

HCO3-

shifts equilibrium to the right and causes acidosis

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16
Q

Can buffer solutions buffer themselves?

A

No

So an increase in CO2 causes both H+ and HCO3 to increase, but HCO3 doesn’t compensate

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17
Q

When is respiratory acidosis

a) compensated
b) uncompensated?

A

a) High CO2, normal pH

b) High CO2, low pH

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18
Q

Which system compensates for respiratory acidosis?

A

Renal

19
Q

What drives bicarbonate reabsorption by the kidneys?

A

H+ secretion by the kidneys

20
Q

How much bicarbonate is reabsorbed by the kidneys in metabolic acidosis?

A

All of it

21
Q

What happens to H+ ions after they are excreted into the renal tubules to drive HCO3- reabsorption?

A

Excreted in urine as titratable acid and ammonium

22
Q

What increases as a result of renal compensation for metabolic acidosis?

A

[HCO3-] reabsorption

and therefore pH increase

23
Q

After the kidneys have compensated for a metabolic acidosis, how do you correct it?

A

Restore normal ventilation

24
Q

What are some causes of respiratory alkalosis?

A

High altitude (conc of oxygen breathed in decreases, rate of body’s removal of CO2 stays the same –> alkalosis)

Hyperventilation

25
Q

What is removed excessively in respiratory alkalosis?

A

CO2

26
Q

What happens as a result of excessive CO2 removal in respiratory alkalosis?

A

H+ and HCO3- decrease

CO2 starts to increase

equilibrium shifts to the left

27
Q

What system compensates for respiratory alkalosis?

A

Renal

28
Q

What happens to H+ secretion in respiratory alkalosis?

A

Decreases, as no CO2 to drive it

29
Q

What happens to bicarbonate reabsorption in metabolic alkalosis?

A

Decreases

As H+ isn’t being secreted to drive it

30
Q

In uncompensated respiratory alkalosis, the urine turns ___.

A

alkaline

31
Q

How is respiratory alkalosis corrected?

A

Restoration of normal breathing

32
Q

What can cause metabolic acidosis?

A

Anything causing H+ excess not related to CO2:

Ingestion of acid

Increased metabolism of acid (anaerobic resp, uncontrolled T1DM)

Loss of bicarbonate - diarrhoea

33
Q

What happens to pH in uncompensated metabolic acidosis?

A

pH decreases

Bicarbonate decreases

34
Q

Why do bicarbonate levels decrease in uncompensated metabolic acidosis?

A

Used up trying to buffer for increased H+

35
Q

What system compensates for metabolic acidosis?

A

Respiratory

36
Q

What senses acidosis with a metabolic cause?

How does the respiratory system compensate for metabolic acidosis?

A

Peripheral chemoreceptors (carotid sinus and aorta)

Hyperventilation

37
Q

How does hyperventilation compensate for metabolic acidosis?

A

Blows off Co2

38
Q

After the resp system has compensated for metabolic acidosis, what happens to bicarbonate levels?

How does the renal system correct this?

A

Decrease further (equilibrium shifts to left)

Secretion of H+ as acid/ammonium

Which drives bicarbonate reabsorption

39
Q

How long do the

a) respiratory
b) renal

systems take to compensate and correct for acid base imbalances?

A

a) Short time

b) Longer

40
Q

What causes metabolic alkalosis?

A

Loss of H+ not related to breathing:

Vomiting - loss of HCl

Ingestion of alkali

Hypersecretion of aldosterone (because K+ and H+ filtration are PAIRED, so H+ is excreted causing an alkalosis)

41
Q

What happens to pH and bicarbonate conc. in uncompensated metabolic alkalosis?

A

pH increases

Bicarbonate conc. increases

42
Q

How does the resp system compensate for metabolic alkalosis?

A

Hypoventilation

retention of CO2, equilibrium shifts to the right

43
Q

How does the renal system correct metabolic alkalosis?

A

Excess of bicarbonate is filtered

No acid generated

Excreted in urine - alkaline