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Flashcards in Physiology Deck (81):
1

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

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

2

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

Intrapleural fluid cohesiveness and negative intrapleural pressure

3

What is intrapleural fluid cohesiveness?

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

4

What does negative intrapleural pressure do?

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

5

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

Active process brought about by the contraction of inspiratory muscles

6

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

Passive process brought about by relaxation of inspiratory muscles

7

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

Elastic connective tissue in the lungs and alveolar surface tension

8

What reduces alveolar surface tension?

Surfactant

9

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

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

10

What is airway resistance determined by?

The radius of the conducting airway

11

What do obstructive diseases cause?

Resistance to airflow, making expiration more difficult than inspiration

12

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

Greater change in pressure

13

What causes increased work of breathing?

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

14

What is anatomical dead space?

Inspired air remaining in the airways

15

When is gas exchange best?

When rates of ventilation and perfusion are the same

16

What is alveolar dead space?

Ventilated alveoli which are not adequately perfused

17

How would you increase airflow if perfusion was greater?

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

18

How would you increase blood flow if airflow was greater?

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

19

Which chemoreceptors detect arterial PaCO2 and pH?

Central and peripheral chemoreceptors

20

Which chemoreceptors detect arterial PO2?

Peripheral chemoreceptors only

21

What is the most important factor detected by chemoreceptors?

PaCO2

22

What does an increased PaCO2 do to ventilation?

Causes an almost linear rise in litres ventilated per min

23

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

Ventilation starts to decrease due to suppression of central respiratory neurones

24

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

Shifts left

25

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

Shifts right

26

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

Respiratory acidosis

27

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

Decreasing (by a lot)

28

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

When it gets below 8kPa

29

What are central chemoreceptors and where are they located?

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

30

What are central chemoreceptors sensitive to?

pH of cerebrospinal fluid

31

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

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

32

What is the pH of cerebrospinal fluid determined by?

PaCO2

33

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

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

34

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

Increased ventilation

35

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

Slow

36

Where are the peripheral chemoreceptors located?

Aortic and carotid bodies

37

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

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

38

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

Around the aortic arch, innervated by the vagus nerve

39

What do carotid bodies respond to?

Increased PaCO2/[H+] or decreased PaO2

40

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

Increased firing rate in the carotid sinus nerve to increase ventilation

41

What is the relative speed of ventilation through peripheral chemoreceptors?

Fast

42

What is hypoxic drive?

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

43

How much oxygen should you give people with hypoxic drive?

23-28%

44

What can increased altitude cause?

Hypocapnia and alkalosis

45

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

Central pattern generator

46

What modulates the central pattern generator?

Feedback from chemoreceptors and lung mechanoreceptors

47

Where is the central pattern receptor?

Pons and medulla

48

What type of neurones does the central pattern receptor have?

Inspiratory and expiratory

49

What is reciprocal inhibition?

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

50

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

Dorsal and ventral respiratory groups

51

What does the dorsal respiratory group contain?

Inspiratory neurones

52

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

Vagus nerve

53

What does the ventral respiratory group contain?

Inspiratory and expiratory neurones- and pre and botzinger complezxes

54

What does the pre-Botzinger complex contain?

Pacemaker neurones which may only be associated with gasping

55

Where is the pneumotaxic centre located?

Pons

56

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

Apeneusis

57

Where are stretch receptors located?

Smooth muscle of bronchial walls

58

What does stimulation of stretch receptors cause?

Inspiration to be shorter and shallower and delays the next cycle

59

What is the pre-Botzinger complex?

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

What is the pneumotaxic centre?

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

61

What is the apneustic centre?

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

62

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

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

63

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

FVC- low, FEV1- low, ratio- normal

64

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

FVC- low, FEV1- low, ratio- low

65

What is physiological dead space?

Alveolar dead space plus anatomical dead space

66

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

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

67

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

CO2 is more soluble in membranes

68

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

Gas exchange problems or right to left shunt in the heart

69

What is the common and uncommon way to transport oxygen?

Common- bound to haemoglobin
Uncommon- dissolved

70

What can oxygen delivery to the tissues be impaired by?

Decreased PaO2
Respiratory disease
Anaemia
Heart failure

71

How many haem groups are in myoglobin?

1

72

What does myoglobin in the blood indicate?

Muscle damage

73

What 3 ways can CO2 be transported?

Bicarbonate (most common), carbamino substances or in solution

74

What respiratory group is associated with inspiration?

Dorsal- fire in bursts to contract inspiratory muscles

75

What is increased firing of dorsal neurones associated with?

Hyperventilation

76

What does increased firing of dorsal neurones cause?

Excites ventral neurones

77

Pneumotaxic centre is stimulated when what neurones fire?

Dorsal

78

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

Generated by medulla but modified by inputs from the pons

79

What do joint receptors do?

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

80

Where is the centre for the cough reflex?

Medulla

81

What adaptations occur as a result of increased altitude?

Increased RBC, 2,3 BPG, capillaries, mitochondria