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Respiratory > Physiology > Flashcards

Physiology Flashcards

1
Q

According to Boyle’s Law, alveolar pressure must be lower than atmospheric pressure for inspiration. How does this happen?

A

1) Chest wall expands
2) Intrapleural pressure falls
3) Increased pressure gradient between the intrapleural space and alveoli
4) Alveoli expand and pressure decreases

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2
Q

What 2 things cause chest wall movement to expand the lungs?

A

Intrapleural fluid cohesiveness and negative intrapleural pressure

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3
Q

What is intrapleural fluid cohesiveness?

A

Water molecules in the intrapleural fluid are attracted to each other and resist being pulled apart

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4
Q

What does negative intrapleural pressure do?

A

Forces the lungs to expand outwards when the chest wall squeezes inwards

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5
Q

What type of process is inspiration and how is it brought about?

A

Active process brought about by the contraction of inspiratory muscles

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6
Q

What type of process is expiration and how is brought about?

A

Passive process brought about by relaxation of inspiratory muscles

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7
Q

In expiration the lungs recoil. How is this brought about?

A

Elastic connective tissue in the lungs and alveolar surface tension

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8
Q

What reduces alveolar surface tension?

A

Surfactant

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9
Q

How would you describe resistance in the lungs and what does this mean?

A

The lungs have very low resistance which means air moves with a small pressure gradient

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10
Q

What is airway resistance determined by?

A

The radius of the conducting airway

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11
Q

What do obstructive diseases cause?

A

Resistance to airflow, making expiration more difficult than inspiration

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12
Q

What is needed to produce a given change in volume when lungs are compliant?

A

Greater change in pressure

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13
Q

What causes increased work of breathing?

A

Decreased compliance and elastic recoil, increased airway resistance and when increased ventilation is required

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14
Q

What is anatomical dead space?

A

Inspired air remaining in the airways

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15
Q

When is gas exchange best?

A

When rates of ventilation and perfusion are the same

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16
Q

What is alveolar dead space?

A

Ventilated alveoli which are not adequately perfused

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17
Q

How would you increase airflow if perfusion was greater?

A

1) Increase CO2
2) Relaxation of airway smooth muscle
3) Dilation of local airways
4) Decreased airway resistance

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18
Q

How would you increase blood flow if airflow was greater?

A

1) Increase O2
2) Relaxation of pulmonary arteriolar smooth muscle
3) Dilation of blood vessels
4) Decreased vascular resistance

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19
Q

Which chemoreceptors detect arterial PaCO2 and pH?

A

Central and peripheral chemoreceptors

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20
Q

Which chemoreceptors detect arterial PO2?

A

Peripheral chemoreceptors only

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21
Q

What is the most important factor detected by chemoreceptors?

A

PaCO2

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22
Q

What does an increased PaCO2 do to ventilation?

A

Causes an almost linear rise in litres ventilated per min

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23
Q

If PaCO2 goes above 10kPa, what happens and why?

A

Ventilation starts to decrease due to suppression of central respiratory neurones

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24
Q

What does metabolic acidosis do to the CO2-ventilation curve?

A

Shifts left

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25
Q

What does metabolic alkalosis do to the CO2-ventilation curve?

A

Shifts right

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26
Q

What does a rise in [H+] ions from increased PCO2 cause?

A

Respiratory acidosis

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27
Q

What has a bigger effect on the CO2-ventilation curve, increasing or decreasing PaO2?

A

Decreasing (by a lot)

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28
Q

When does a decreasing PaO2 begin to have an effect on ventilation?

A

When it gets below 8kPa

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29
Q

What are central chemoreceptors and where are they located?

A

Diffuse collection of neurones which are located near the ventrolateral surface of the medulla

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30
Q

What are central chemoreceptors sensitive to?

A

pH of cerebrospinal fluid

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31
Q

What is the blood brain barrier impermeable to? Give examples of what can’t/can pass through.

A

Polar substances- H+ and HCO3- cannot pass through but CO2 can

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32
Q

What is the pH of cerebrospinal fluid determined by?

A

PaCO2

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33
Q

What is significant about the CSF not being a good buffer?

A

Small changes in PaCO2 can have a big effect on the pH

34
Q

What does the stimulation of the central chemoreceptor by decreased CSF pH/increased PaCO2 cause?

A

Increased ventilation

35
Q

What is the relative speed of increased ventilation through central chemoreceptors?

A

Slow

36
Q

Where are the peripheral chemoreceptors located?

A

Aortic and carotid bodies

37
Q

Where specifically are peripheral chemoreceptors at the carotid body and what are they innervated by?

A

Bifurcation of the common carotid, above the coronary sinus. Innervated by the carotid sinus nerve into the glossopharyngeal nerve

38
Q

Where specifically are peripheral chemoreceptors at the aortic body and what are they innervated by?

A

Around the aortic arch, innervated by the vagus nerve

39
Q

What do carotid bodies respond to?

A

Increased PaCO2/[H+] or decreased PaO2

40
Q

How do carotid bodies respond to increased PaCO2/[H+] or decreased PaO2?

A

Increased firing rate in the carotid sinus nerve to increase ventilation

41
Q

What is the relative speed of ventilation through peripheral chemoreceptors?

A

Fast

42
Q

What is hypoxic drive?

A

Loss in sensitivity to increased PaCO2 and ventilation is therefore controlled by PaO2

43
Q

How much oxygen should you give people with hypoxic drive?

A

23-28%

44
Q

What can increased altitude cause?

A

Hypocapnia and alkalosis

45
Q

What is the part in the brainstem which sets the basic rhythm and pattern of breathing and controls respiratory muscles?

A

Central pattern generator

46
Q

What modulates the central pattern generator?

A

Feedback from chemoreceptors and lung mechanoreceptors

47
Q

Where is the central pattern receptor?

A

Pons and medulla

48
Q

What type of neurones does the central pattern receptor have?

A

Inspiratory and expiratory

49
Q

What is reciprocal inhibition?

A

Activity of inspiratory neurones inhibits activity of expiratory neurones and vice versa

50
Q

What are the 2 groups of respiratory neurones in the medulla?

A

Dorsal and ventral respiratory groups

51
Q

What does the dorsal respiratory group contain?

A

Inspiratory neurones

52
Q

How does the dorsal respiratory group receive impulses from the central and peripheral chemoreceptors?

A

Vagus nerve

53
Q

What does the ventral respiratory group contain?

A

Inspiratory and expiratory neurones- and pre and botzinger complezxes

54
Q

What does the pre-Botzinger complex contain?

A

Pacemaker neurones which may only be associated with gasping

55
Q

Where is the pneumotaxic centre located?

A

Pons

56
Q

What happens if there is an absence of vagal input and sectioning of the midpons?

A

Apeneusis

57
Q

Where are stretch receptors located?

A

Smooth muscle of bronchial walls

58
Q

What does stimulation of stretch receptors cause?

A

Inspiration to be shorter and shallower and delays the next cycle

59
Q

What is the pre-Botzinger complex?

A

A network of neurones which controls the basic rhythm of breathing- they display pacemaker activity and are located near the upper end of the medullary respiratory centre

60
Q

What is the pneumotaxic centre?

A

Stimulation of this terminates inspiration when dorsal neurones fire. Without this mechanism, breathing is prolonged inspiratory gasps known as apneusis

61
Q

What is the apneustic centre?

A

Impulses from neurones here excite the inspiratory area of the medulla and prolong inspiration

62
Q

What would the FVC/FEV1/ratio be for an obstructive disease?

A

FVC- low (COPD)/high (asthma), FEV1- low, ratio- low

63
Q

What would the FVC/FEV1/ratio be for a restrictive disease?

A

FVC- low, FEV1- low, ratio- normal

64
Q

What would the FVC/FEV1/ratio be for a combination disease?

A

FVC- low, FEV1- low, ratio- low

65
Q

What is physiological dead space?

A

Alveolar dead space plus anatomical dead space

66
Q

What are the 4 factors which influence the rate of gas exchange across the alveolar membrane?

A

Partial pressure gradient of O2 and CO2, diffusion coefficient for O2 and CO2, surface area of and thickness of alveolar membrane

67
Q

Why does CO2 have a smaller partial pressure gradient than O2?

A

CO2 is more soluble in membranes

68
Q

What would a big different in gradient between PaCO2 and PaO2 suggest?

A

Gas exchange problems or right to left shunt in the heart

69
Q

What is the common and uncommon way to transport oxygen?

A

Common- bound to haemoglobin

Uncommon- dissolved

70
Q

What can oxygen delivery to the tissues be impaired by?

A

Decreased PaO2
Respiratory disease
Anaemia
Heart failure

71
Q

How many haem groups are in myoglobin?

A

1

72
Q

What does myoglobin in the blood indicate?

A

Muscle damage

73
Q

What 3 ways can CO2 be transported?

A

Bicarbonate (most common), carbamino substances or in solution

74
Q

What respiratory group is associated with inspiration?

A

Dorsal- fire in bursts to contract inspiratory muscles

75
Q

What is increased firing of dorsal neurones associated with?

A

Hyperventilation

76
Q

What does increased firing of dorsal neurones cause?

A

Excites ventral neurones

77
Q

Pneumotaxic centre is stimulated when what neurones fire?

A

Dorsal

78
Q

Where is rhythm of breathing generated and where is it modified?

A

Generated by medulla but modified by inputs from the pons

79
Q

What do joint receptors do?

A

Impulses from moving limbs increases breathing- contributes to increased ventilation during exercise

80
Q

Where is the centre for the cough reflex?

A

Medulla

81
Q

What adaptations occur as a result of increased altitude?

A

Increased RBC, 2,3 BPG, capillaries, mitochondria

Respiratory (16 decks)

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