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The Respiratory System > Mechanisms and Regulation of Breathing > Flashcards

Mechanisms and Regulation of Breathing Flashcards

1
Q

What is the order of structures from the trachea to the alveoli

A

Trachea - bronchi - bronchioles - alveoli

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2
Q

What surrounds the walls of alveoli

A

Elastin fibres

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3
Q

What does elastin allow

A

It allows recoil of the alveoli at the end of a normal breath. The alveoli can return to their normal shape and size.

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4
Q

In what direction does lung elastic recoil occur

A

Lung elastic recoil occurs inwards

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5
Q

In what direction does the chest elastic recoil occur

A

Chest elastic recoil occurs outwards.

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6
Q

What is it that means the lungs do not collapse

A

There ate equal and opposing forces outwards and inwards. The lungs recoil inwards and the chest recoils outwards at the end of a normal breath.

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7
Q

On inspiration is the pressure in the atmosphere or the alveolus greater

A

The pressure in the atmosphere is much greater than that in the alveoli. This allows gas to enter the lungs and inspiration to occur.

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8
Q

What happens to the diaphragm and external intercostal muscles on inspiration

A

The diaphragm relaxes and the external intercostal muscles contract to increase chest volume and decrease alveolar pressure to allow for the entry of air.

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9
Q

What is the mechanism of expiration

A

The pressure in the alveoli must be greater than that in the atmosphere to force air out of the alveoli. This happens as the lungs recoil inwards at the end of a normal breath (which is a passive process).

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10
Q

What takes longer, inspiration or expiration

A

The expiratory time is longer than the inspiratory time.

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11
Q

How is large or forced expiration different than normal

A

It is an active process. Normal expiration is passive and occurs due to elastic recoil.

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12
Q

What muscles are involved in large or forced expiration

A

The abdominal muscles contract to push the diaphragm upwards towards its normal dome configuration and internal intercostal muscles also contract.

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13
Q

What is the tidal volume

A

The depth of the inspiration-expiration wave form

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14
Q

What is the normal tidal volume in a healthy person

A

400ml to 800ml.

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15
Q

What is an abnormal respiratory frequency

A

Above 20 breaths per minute.

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16
Q

What is the minute ventilation

A

The tidal volume multiplied by the respiratory rate in litres per minute.

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17
Q

What is the normal minute ventilation

A

5 litres per minute.

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18
Q

What structure is the respiratory rhythm regulated by

A

The medulla

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19
Q

What is the most important part of the brain for the regulation of breathing

A

The medulla. If this was taken away breathing would stop all together.

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20
Q

What control are the medulla and pons under

A

Autonomic control

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21
Q

What control is the cortex under

A

Voluntary control

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22
Q

What would happen to the breathing rhythm is the cortex was removed

A

Rhythmical breathing continues but cannot be adjusted voluntarily.

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23
Q

What is the action of expiratory medullary neurons on inspiratory medullary neurons

A

Expiratory medullary neurons inhibit the inspiratory medullary neurons.

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24
Q

What is the action of inspiratory medullary neurons on expiratory medullary neurons

A

Inspiratory medullary neurons activate expiratory medullary neurons

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25
Q

What does exaggerated inspiration lead to

A

Exaggerated expiration

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26
Q

What are four tings which change the basic breathing pattern

A
  • Inhalation of noxious substances
  • Sleep
  • Exercise
  • Speech
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27
Q

Where do feedback inputs come from for respiratory rhythm

A

Lung receptors and chemoreceptors

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28
Q

What are the three types of lung receptors

A
  • Slowly adapting receptors
  • Rapidly adapting receptors
  • C-fibre endings.
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29
Q

What are the two types of chemoreceptors

A
  • Central chemoreceptors

- Peripheral chemoreceptors

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30
Q

What are lung receptors sensitive to

A

Neurological input from the vagus nerve

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31
Q

What are chemoreceptors sensitive to

A

Chemical changes such as changes in oxygen and carbon dioxide concentrations.

32
Q

What is the difference in response to CO2 levels in central and peripheral chemoreceptors

A

Central chemoreceptors respond slowly to arterial carbon dioxide concentration while peripheral chemoreceptors respond rapidly to changes in arterial carbon dioxide.

33
Q

What happens if you remove the feedback through the vagus nerve from the lungs

A

Breathing becomes slow and deep.

34
Q

What happens if you stimulate the vagus nerve

A

Breathing is rapid and shallow.

35
Q

What is an example of a slowly adapting receptor in the lungs

A

Stretch receptors

36
Q

What do stretch receptors do

A

They are receptive to mechanical strain and are slow firing. They help to initiate expiration and prevent over inflation of the lungs.

37
Q

What is meant by “The Hering-Breuer Inflation Reflex”

A

prolonged inspiration leads to prolonged expiration.

38
Q

How are rapidly firing receptors different to slowly adapting receptors

A

They set off a burst of firing and are not regularly continuous over a long period of time.

39
Q

What do rapidly firing receptors do

A

They initiate cough and bronchoconstriction.

40
Q

Which fibres are myelinated

A

Afferent fibres for rapdidly adapting receptors and afferent fibres for slowly adapting receptors.

41
Q

Which fibres are not myelinated

A

C-fibres

42
Q

How are C-fibres stimulated

A

By increased interstitial fluid (oedema) and inflammatory mediators. they are sensitive to inflammation in the lungs.

43
Q

Where is the site that signals are relayed to the medulla

A

The bifurcation of the common carotid arteries

44
Q

What nerve are signals sent through to the medulla from the site at the bifurcation of the common carotid arteries

A

The glossopharyngeal nerve.

45
Q

Which nerve are signals from the arch of the aorta relayed through to the medulla

A

The vagus nerve

46
Q

What is the action of central chemoreceptors on the medulla when there is increased carbon dioxide

A

They act indirectly by acidifying cerebrospinal fluid and causing breathing to change by increased ventilation to get rid of the excess carbon dioxide.

47
Q

What is the normal arterial oxygen

A

Around 13/14kPa.

48
Q

At what partial pressure does low oxygen become significant

A

Below 8kPa as the saturation of haemoglobin begins to fall.

49
Q

Why would you not give high flow oxygen to a patient with COPD who has chronic hypoxia

A

Because the drive for this person to breathe comes from the low concentration to oxygen since the normal sensitivity to high carbon dioxide levels is reduced. Giving oxygen means that the drive to breathe no longer exists so there is hypoventilation and a further increase in arterial CO2. This can lead to death.

50
Q

What is obstructive sleep apnoea

A

the drive to breathe during the day comes from the midbrain neural activity which also controls the muscles of the upper airway. At night the drive to breathe decreases and as a result people can also lose control of their upper airway, meaning it can come restricted or obstructed. This is obstructive sleep apnoea.

51
Q

What are the two types of muscle activity in the upper airway

A

Phasic activity and tonic activity

52
Q

What happens in phasic activity of the upper airway

A

There is contraction of the upper airway muscles, opening of the upper airway and facilitation of inward flow.

53
Q

What happens in tonic activity

A

There is continuous background activity.

54
Q

Why may the upper airways collapse during sleep

A

There is loss of tonic activity of the upper airway.

55
Q

What are some examples of drugs which are breathing suppressants

A
  • Almost all anaesthetics
  • Analgesics
  • Sedatives - e.g. benzodiazapines.
56
Q

What are examples of breathing stimulants

A

Direct breathing stimulants include doxapram and indirect include beta 2 agonists such as bronchodilators.

57
Q

What is the alveolar pressure compared to the atmospheric pressure at the end of a normal breath out

A

At the end of a normal breath out the alveolar and atmospheric pressures are equal as there is an open connection between them and there is no airflow in or out of the lungs at this point.

58
Q

Why does the chest wall have elastic recoil outwards at the end of a normal breath

A

To resist distortion inwards from its natural resting shape.

59
Q

What are the two inspiratory muscles

A

The diaphragm and the external intercostal muscles.

60
Q

On inspiration is the pleural pressure positive or negative relative to the atmospheric pressure

A

The pleural pressure becomes more negative than the atmospheric pressure and this negative pressure is transmitted to the alveoli.

61
Q

In which direction does air flow on inspiration and why does this happen

A

Air flow into the lungs down the pressure gradient between the mouth and the alveoli.

62
Q

Is the pressure in the alveoli positive or negative upon expiration

A

On expiration, the pressure in the alveoli is positive (compared to it being negative on expiration).

63
Q

In which direction does air move on expiration and why does this happen

A

Air moves from the alveoli to the mouth down a pressure gradient. On expiration the pressure in the alveoli is greater than that in the atmosphere.(this is compared to inspiration where the pressure in the atmosphere is greater than that in the alveoli).

64
Q

What are the two expiratory muscles (for forced or large expiration)

A

The internal intercostal muscles and the abdominal muscles.

65
Q

What limits the maximum airflow in expiration

A

Compression of small intrapulmonary airways by surrounding alveoli.

66
Q

What controls the rhythmical contraction and relaxation of the respiratory muscles

A

The central nervous system.

67
Q

What would happen to breathing if the upper pons region of the brain was removed

A

This would result in slow, gasping breaths.

68
Q

What is it thought that neurons in the upper pons region do

A

Help to control breathing

69
Q

What would happen on complete removal of the pons

A

This would restore rhythmical breathing.

70
Q

Where is the basic rhythm of breathing generated

A

The medulla

71
Q

What are the three groups of respiratory neurons in the medulla and pons

A
  • The ventral respiratory group (VRG)
  • The dorsal respiratory group (DRG)
  • The pontine respiratory group (PRG)
72
Q

Which types of neurons for breathing are in the ventral respiratory group

A

Both expiratory and inspiratory neurons.

73
Q

Which types of neurons for breathing are in the dorsal respiratory group

A

Predominantly inspiratory neurons.

74
Q

Which types of neurons for breathing are in the pontine respiratory group

A

Neurons active in both inspiratory and expiratory phases.

75
Q

What is the functional model of the mechanism of breathing

A
  • Discharge from the inspiratory neurons activates the respiratory muscles via spinal motor nerves resulting in inspiration.
  • Expiratory neurons fire and inhibit the inspiratory neurons.
  • Nerve impulses to the inspiratory muscles stop and passive expiration occurs.
  • If forceful expiration is required, expiratory neuron activity also activates expiratory muscles.
    INSPIRATORY NEURONS ACTIVATE EXPIRATORY NEURONS
    EXPIRATORY NEURONS INHIBIT INSPIRATORY NEURONS.
76
Q

Where are central chemoreceptors located

A

The ventrolateral surface of the medulla

77
Q

Where are peripheral chemoreceptors located

A

Carotid bodies.

The Respiratory System (20 decks)

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