Resp > Session 4.2 > Flashcards

Session 4.2 Flashcards

(52 cards)

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1
Q

What is the normal range of pCO2?

A

4.7 - 6.0 kPa

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2
Q

What is the normal range for pO2?

A

9.3 - 13.3 kPa

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3
Q

What is the normal range for bicarbonate?

A

22 - 26 mmol/L

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4
Q

What is the normal pH range in the body?

A

7.35 - 7.45

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5
Q

What is the function of the respiratory system?

A

Maintain oxygen and carbon dioxide partial pressure gradients to optimise transfer
Regulate pH of extracellular fluid

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6
Q

Define Hypercapnia

A

Rise in pCO2

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7
Q

Define hypocapnia

A

Fall in pCO2

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8
Q

Define hypoxia

A

Fall in pO2

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9
Q

What happens to the partial pressure of PCO2 and PO2 in exercise?

A

pO2 drops and pCO2 rises
This is because you are using up oxygen and making carbon dioxide.
Breathing more restores both - because you breathe in more oxygen and breathe off more CO2.

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10
Q

Define hyperventilation

A

Ventilation increase without change in metabolism

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11
Q

What happens to the pO2 and pCO2 levels when you hyperventilate?

A

pO2 will rise

pCO2 will fall

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12
Q

Define hypoventillation

A

Ventilation decrease without change in metabolism

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13
Q

What happens to the pO2 and pCO2 levels during hypoventilation

A

pO2 will fall

pCO2 will rise

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14
Q

What would happen if the pO2 changes without a change in pCO2?

A

Correction of pO2 will cause the pCO2 to drop. Therefore leading to hypocapnia.

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15
Q

Which can we tolerate better - changes in pO2 or changes in pCO2?

A

Changes in pO2

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16
Q

What is the buffer system present in the blood?

A

Carbonic acid - bicarbonate buffer system

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17
Q

What is the pH of plasma determined by?

A

Crucially therefore the pH of plasma is determined by the ratio of [HCO3-] to pCO2 which is normally about 20:1.

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18
Q

What happens to the pH if the pCO2 increases an the HCO3 stays the same

A

pH will decrease

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19
Q

What happens to the pH if the pCO2 decreases and the HCO3- stays the same?

A

pH will rise

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20
Q

What is the normal range of pH?

A

7.35 - 7.45

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21
Q

What happens if the pH falls below 7.0?

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A

Enzymes become denatured

22
Q

What happens if the pH rises above 7.6?

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A

Free calcium concentration drops leading to tetany (which is where you get involuntary muscle contractions)

23
Q

How does reduced ventilation influence plasma pH?

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A

Hypoventilation leads to increase pCO2
Hypercapnia leads to fall in plasma pH
Respiratory acidosis

24
Q

How does increases ventilation influence plasma pH

Study These Flashcards
A

Hyperventilation leads to decrease in pCO2
Hypocapnia leads to rise in plasma pH
Respiratory alkalosis

25
What does plasma pH depend on?
The ratio of bicarbonate to pCO2 (not their absolute values)
26
How is the kidney involved controlling plasma pH?
The kidney controls bicarbonate
27
How is respiratory acidosis compensated?
By the kidneys increase bicarbonate
28
How is respiratory alkalosis compensated?
By the kidneys decreasing bicarbonate
29
How can you tell if something is fully compensated or partially compensated?
If it is fully compensated, the pH will be within the normal range. If it is partially compensated, the pH will not be in the normal range
30
What is metabolic alkalosis?
If plasma bicarbonate rises Plasma pH rises Metabolic alkalosis
31
What can cause the plasma bicarbonate to rise?
Vomiting - this gets rid of lots of protons (hydrogen ions)
32
Compare the compensation of respiratory driven changes to pH with that of metabolic changes to pH?
Respiratory driven changes are compensated by the kidney | Metabolic changes in pH area driven by breathing
33
Describe the key features of respiratory acidosis
pH decreased pCO2 increase HCO3- normal or increase
34
Describe the key features of metabolic acidosis
pH decreased pCO2 normal or decreased HCO3 - decreased
35
Describe the key features of respiratory alkalosis
pH increased pCO2 decreased HCO3 - normal or decreased
36
Describe the key features of metabolic alkalosis
pH increased pCO normal or increased HCO3 - increased
37
Which is more critical to control - pO2 or pCO2?
pCO2 is more critical to control
38
What are the different sensors that detect changes in the pH?
- Central chemoreceptors - Peripheral chemoreceptors - Pulmonary receptors - Joint and muscle receptors
39
What do the central chemoreceptors detect?
H+ ions
40
Where are the central chemoreceptors found?
Located on the ventral surface of the medulla and exposed to the CSF
41
If the arterial pCO2 were to rise, how would the central chemoreceptors respond?
If pCO2 rises, the ventilation would increase (stimulate breathing) to lower the pCO2 ie you would blow off more carbon dioxide. This would result in the pCO2 being normal again.
42
What do the central chemoreceptors detect?
They detect changes in arterial pCO2
43
What is the pH of CSF determined by?
Determined but the activity of choroid plexus cells which pump bicarbonate into and out of the CSF (as there is no haemoglobin). It is largely independent of the plasma bicarbonate. CSF dissolved CO2 is determined by the plasma dissolved CO2.
44
What cells in the CSF are responsible for the movement of bicarbonate?
Choroid plexus cells
45
What is the CSF pCO2 determined by?
Arterial pCO2
46
Which is corrected more quickly - CSF pH or plasma pH?
CSF pH because of its smaller volume
47
How is it that the CSF pH is independent of the plasma pH?
The blood brain barrier prevent H+ and HCO3- from affecting the CSF.
48
What cells are responsible for maintaining the blood brain barrier?
Pericytes and astrocytes
49
Can Co2 cross the blood brain barrier?
Yes
50
Describe the response of the central chemoreceptors on an increase in pCO2?
- Increases pCO2 drives CO2 across the blood Brian barrier - CSF bicarbonate initially constant - CSF pH falls - Fall in CSF pH detected by central chemoreceptors - Drives increased ventilation - Inc ventilation lowers pCO2 - This restores CSF pH
51
What sensors are responsible for detecting hypoxia?
Peripheral chemoreceptors
52
What happens to the CSF plasma during persisting hypoxia?
- Hypoxia detected by peripheral chemoreceptors - Increased ventilation - But CO2 will fall further - CSF compensates for the altered pCO2 - Choroid plexus selectively did H+ or HCO3- into CSF - Central chemoreceptors ‘accept’ the pCO2 as normal

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