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HUBS192 2024 > Lecture 19: O2 and CO2 TRANSPORT > Flashcards

Lecture 19: O2 and CO2 TRANSPORT Flashcards

1
Q

How is oxygen carried in the blood?

A

Dissolved in the plasma and bound to haemoglobin in RBC’s (most effective)

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2
Q

How much oxygen is dissolved in a litre of blood?

A

3mL so about 15mL in body but we need about 250mL/min

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3
Q

What does oxygen do?

A

Form an easily reversible combination with Hb to give oxyhaemoglobin

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4
Q

What does binding of oxygen depend on?

A

The partial pressure of oxygen

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5
Q

What is haemoglobin saturation?

A

The percentage of heme units containing bound oxygen at any given moment

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6
Q

What is the average partial pressure of oxygen of blood entering the systemic circuit?

A

High (95-100mmHg)

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7
Q

What is the average partial pressure of oxygen of blood leaving peripheral tissues (venous blood)?

A

Moderate (40-50mmHg)

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8
Q

What is the average partial pressure of oxygen in active muscle tissue?

A

Low (10-20mmHg)

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9
Q

What is the shape of the oxygen haemoglobin saturation curve?

A

Sigmoidal, not linear

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10
Q

What happens when the slope of the saturation curve is steep?

A

A very small change in partial pressure of oxygen in the blood will result in a large change in the amount of oxygen bound to haemoglobin or released from oxyhemoglobin. oxygen binding affinity is decreased

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11
Q

What happens in the flat part of the saturation curve?

A

Large changes in partial pressure of oxygen will result in small changes in the percentage of oxyhaemoglobin

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12
Q

What does the curve vary with?

A

Conditions to improve oxygen uptake and delivery

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13
Q

What shifts the curve right?

A

Reduced pH (Bohr’s effect), increased partial pressure of carbon dioxide and increased temperature

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14
Q

What shifts the curve left?

A

Increased pH (Bohr’s effect), decreased partial pressure of carbon dioxide and decreased temperature

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15
Q

How is carbon dioxide transported?

A

Dissolved in plasma (7%), as bicarbonate (70%) and combined with proteins as carbamino compounds (23%)

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16
Q

What does 70% if carbon dioxide do?

A

It is converted to carbonic acid by activity of enzyme carbonic anhydrase

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17
Q

What do the carbonic acid molecules do?

A

Immediately dissociate into a hydrogen ion and bicarbonate ion

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18
Q

What do the hydrogen ions do?

A

Bind to haemoglobin forming HbH+

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19
Q

What do the bicarbonate ions do?

A

Move into plasma in exchange for chloride ions (Cl-). Process called the chloride shift

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20
Q

What do we need to maintain?

A

Normal levels of oxygen and carbon dioxide for metabolic and biochemical stability

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21
Q

What is variable?

A

Oxygen usage and carbon dioxide production but despite this, oxygen and carbon dioxide are kept within close limits

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22
Q

What is the control centre?

A

Pons, medulla oblongata and other parts of the brain

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23
Q

What does the control centre receive?

A

Afferent signals from sensors

24
Q

What are the sensors?

A

Chemoreceptors, baroreceptors, lung stretch receptors and protective reflexes

25
Q

What does the control centre send?

A

Efferent signals to effectors

26
Q

What are the effectors?

A

Muscles of respiration

27
Q

What can the higher centres do?

A

Alter the activity of the pneumotaxic centres

28
Q

Where are the higher centres?

A

Cerebral cortex, limbic system and hypothalamus

29
Q

What do the apneustic and pneumotaxic centres do?

A

Adjust the output of the respiratory rhythmicity centres

30
Q

What do apneustic centres do?

A

Promote inhalation by stimulating DRG (dorsal respiratory group)

31
Q

What do the pneumotaxic centres do?

A

Inhibit apneustic centres

32
Q

Where are the apneustic and pneumotaxic centres?

A

In the pons

33
Q

What do the respiratory rhythmicity centres do?

A

Generate cycles of contraction and relaxation in the diaphragm, establishing pace of respiration, modify activity in response to chemical and pressure signals

34
Q

What does the dorsal respiratory group of neurons (DRG) have?

A

An inspiratory centre

35
Q

What does the DRG do?

A

Send signals to inspiratory muscles (diaphragm and external intercostals)

36
Q

What is the pre-botzinger complex?

A

A pace maker/rhythm generator

37
Q

What does the ventral respiratory group of neurons (VRG) have?

A

Inspiratory and expiratory centres

38
Q

What does the VRG do?

A

Sends signals to accessory inspiratory and expiratory muscles

39
Q

What respiratory centre can’t be damaged?

A

Respiratory rhythmic centres

40
Q

What is part of the respiratory rhythmic centres?

A

VRG, DRG and pre-botzinger complex

41
Q

What are the most important receptors in determining respiratory activity?

A

Carbon dioxide receptors (chemoreceptors)

42
Q

Where are peripheral chemoreceptors?

A

Carotid artery and aortic arch

43
Q

Where are the central chemoreceptors?

A

Medulla oblongata

44
Q

What is increasing arterial partial pressure of carbon dioxide called?

A

Hypercapnia

45
Q

What also happens in hypercapnia?

A

Decreased pH

46
Q

What is decreasing arterial partial pressure of carbon dioxide called?

A

Hypocapnia

47
Q

What also happens in hypocapnia?

A

Increased pH

48
Q

What is the result of hypercapnia?

A

Respiratory muscles stimulated, increased respiratory. rate with increased elimination of carbon dioxide at the alveoli

49
Q

What is the result of hypocapnia?

A

Respiratory muscles inhibited, decreased respiratory rate with decreased elimination of carbon dioxide at the alveoli

50
Q

What are baroreceptors?

A

Blood pressure sensors that also affect respiratory function

51
Q

What happens when arterial blood pressure goes down?

A

Reduced flow, sensed by the baroreceptors, respiratory minute volume goes up and increased uptake of air

52
Q

What happens when arterial blood pressure goes up?

A

Increased flow, sensed by the baroreceptors, respiratory volume goes down and decreased uptake of air

53
Q

What do the lung stretch (inflation/deflation) receptors do?

A

They send afferent input as the lungs inflate or deflate

54
Q

What does the brain do once it receives afferent input from the lung stretch receptors?

A

Sends efferent output preventing them from stretching too far either way

55
Q

What do protective reflexes do?

A

Detect irritation

56
Q

What does the brain do once it receives information from the protective reflexes?

A

Sends efferent signal that triggers a sneeze or cough

HUBS192 2024 (38 decks)

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