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PHGY 210 > Respiration lecture 5 > Flashcards

Respiration lecture 5 Flashcards

1
Q

What is respiratory failure?

A

when the respiratory system is unable to do it’s job properly

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2
Q

What are the 3 ways respiratory failure can occur?

A
  1. failure of the gas-exchanging capabilities of the lungs
  2. Failure of the neural control of ventilation
  3. Failure of the neuromuscular breathing apparatus
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3
Q

What is blood hypoxia?

A

deficient blood oxygenation described as low PaO2 and low percentage of Hb saturation

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4
Q

What are the 5 general causes of hypoxia?

A
  1. Inhalation of low PO2 (high altitude)
  2. Hypoventilation
  3. Ventilation/perfusion imbalance in the lungs
  4. Shunts of blood across the lungs
  5. O2 diffusion impairment
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5
Q

What happens to PaO2 and PaCO2 during hypoventilation?

A

PaO2 decreases and PaCO2 increases

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6
Q

How does hypoventilation happen?

A

It’s when the alveolar ventilation in relation to the metabolic CO2 production reduces

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7
Q

What happens to venous blood during shunts of blood across the lungs?

A

Venous blood bypasses the gas-exchanging area and returns to the systemic circulation deoxygenated.

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8
Q

What is an example of shunts of blood across the lungs?

A

patent foramen ovale

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9
Q

What are 2 examples of O2 diffusion impairment?

A

THickening of the alveolar/capillary membrane or pulmonary edema

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10
Q

What kind of control is breathing under?

A

Voluntary and autonomic control

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11
Q

Which neurological structures control voluntary breathing?

A

Cerebral hemispheres

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12
Q

Which neurological structures control involuntary breathing?

A

Brainstem: pons and medulla

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13
Q

What happens when you stop ventilation voluntarily?

A

the involuntary system will take over and you will start breathing again

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14
Q

What is the breaking point?

A

It is when voluntary control is over-ridden when PACO2 and PAO2 have reached certain levels

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15
Q

What does over-riding of the voluntary control by the automatic control depend upon?

A

the information from the receptors sensitive to CO2 and O2 levels in arterial blood and CSF

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16
Q

What are the 3 basic elements in the respiratory control system?

A

Sensors, controllers and effectors

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17
Q

What is the function of sensors?

A

They gather information about the lung volume and CO2/O2 levels

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18
Q

What are the two kinds of sensors?

A

Pulmonary receptors and chemoreceptors

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19
Q

How is information sent to controllers?

A

Via neural fibres

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20
Q

Where are controllers located?

A

in the pons and medulla

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21
Q

What happens when information has reached the pons and medulla?

A

the peripheral information and inputs from the higher structures of the CNS are integrated

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22
Q

What is another name for effectors?

A

respiratory muscles

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23
Q

Why are neuronal impulses sent to effectors?

A

so that ventilation can be adjusted to the person’s metabolic needs determined by the sensors and controllers

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24
Q

Where are the pacemakers cells located?

A

the ventral respiratory group of the medulla

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25
Q

What is the function of the ventral respiratory group of the medulla?

A

To generate the basic rhythm of breathing

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26
Q

What does the ventral respiratory group contain?

A

pacemaker cells

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27
Q

What is the function of the dorsal respiratory group?

A

it receives several sensory inputs

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28
Q

What do the cells in the ventral and dorsal respiratory group connect to?

A

inspiratory motor neurons

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29
Q

What kind of cells are found in the medulla?

A

pacemaker cells

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30
Q

What does the medulla do? how is it affected in the absence of the vagus nerve?

A

It generates the basic respiratory rhythmicity. Without the vagus nerve, the rhythmicity is the same but with no control of the lung volume

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31
Q

What is the function of the upper pons?

A

it modifies the inspiratory activity of the centres in the medulla

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32
Q

Does the upper pons turn on or turn off inspiration?

A

turn off

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33
Q

What happens to the tidal volume and breathing frequency when the upper pons turn off inspiration (when the upper pons are functioning)?

A

tidal volume: becomes smaller
breathing frequency: increases

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34
Q

What happens to breathing when the upper pons are cut?

A

Breathing becomes slow and deep (no more inhibition of inspiration)

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35
Q

What happens to breathing when the vagus nerves are cut on an intact brainstem?

A

It has the same effect as removing the upper pons meaning that breathing will be slow and deep

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36
Q

What s the function of the cells located in the lower pons?

A

They send excitatory impulses to the respiratory groups of the medulla

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37
Q

What does the lower pons promote?

A

They promote inspiration

38
Q

What happens when you remove the upper pons and the vagus nerve?

A

It causes apneuses, seen in some severe types of brain injuries

39
Q

What is apneuses?

A

tonic inspiratory activity interrupted by short expirations –> prolonged inspiratory phase followed by an irregular and inadequate expiration

40
Q

What do chemoreceptors detect?

A

PO2, PCO2 and pH in arterial blood

41
Q

Where is information from the chemoreceptors carried to?

A

the respiratory neurons

42
Q

When will the activity of respiratory neurons increase?

A

if PaO2 is lower than 60 mmHg
if PaCO2 is greater than 40 mmHg

43
Q

When will the activity of respiratory neurons decrease?

A

if PaO2 is greater than 100 mmHg
if PaCO2 is lower than 40 mmHg

44
Q

What are the two kinds of chemoreceptors?

A

Central chemoreceptors and Peripheral chemoreceptors

45
Q

Where are central chemoreceptors located?

A

in the ventral surface of the medulla

46
Q

What do the central chemoreceptors detect?

A

the pH of CSF

47
Q

What is the pH and PCO2 of the CSF surrounding the central chemoreceptors influenced by?

A

by the pH and PCO2 of the arterial blood

48
Q

What do the central chemoreceptors give rise to?

A

the main drive to breathe under normal conditions

49
Q

How can the sensitivity of central chemoreceptors be assessed?

A

with a CO2 rebreathing test

50
Q

What happens during a CO2 rebreathing test?

A

Breathing different mixtures of CO2 or rebreathing expired from a bag filled with O2

51
Q

What happens when the chemoreceptors are stimulated during the CO2 rebreathing test?

A

When the pH of the CSF is reduced due to increased CO2, the chemoreceptors are stimulated to increase ventilation

52
Q

What kind of relationship is there between ventilation and PCO2 in central chemoreceptors?

A

it is a linear relationship where minute ventilation will increase as soon as PaCO2 increases

53
Q

From the variables responsible for minute ventilation (Ve=Tv x frequency), which is responsible for increased minute ventilation when PCO2 is elevated?

A

The tidal volume and the frequency increases

54
Q

How do the chemoreceptors work?

A

Only the CO2 can cross the blood-brain barrier and go into the CSF. Once it has crossed it will go through reactions to make HCO3- and H+. This will decrease the pH of CSF detected by the receptors and increase ventilation. (vice-versa)

55
Q

What are peripheral chemoreceptors mainly sensitive to?

A

changes in PO2

56
Q

What are peripheral chemoreceptors secondarily stimulated by?

A

increases PCO2 and decreased pH

57
Q

Where are peripheral chemoreceptors located?

A

in the carotid bodies and the aortic bodies

58
Q

What are the carotid and aortic bodies made up of?

A

blood vessels structural supporting tissue and nerve ending of sensory neurons

59
Q

What two nerves make up the carotid and aortic bodies?

A

Carotid: glossopharyngeal nerve (IX)
Aortic: vagus nerve (X)

60
Q

Where do the afferent fibers of the peripheral chemoreceptors projected?

A

the the dorsal group of the respiratory neuron in the medulla

61
Q

How can the sensitivity of peripheral chemoreceptors be assessed?

A

by having subjects breathe gas mixtures with decreased concentrations of O2

62
Q

What pressure does O2 have to be to have an appreciable change in minute ventilation when PCO2 is not increased?

A

60 mmHg

63
Q

Increasing PCO2, ___ ventilation at ___

A

increases
any PO2

64
Q

An ___ in PCO2 and a ___ in PO2 interact giving an augmented ventilatory response

A

increase
decrease

65
Q

What are the 3 kinds of receptors in the lungs that respond to mechanical stimuli?

A

Pulmonary stretch receptors
Irritant receptors
Juxta-capillary receptors (J receptors)

66
Q

Where do the afferent fibres of the receptors that respond to mechanical stimuli travel?

A

in the vagus nerve

67
Q

Where are pulmonary stretch receptors located?

A

in the smooth muscle of the trachea down to the terminal bronchioles

68
Q

What are pulmonary stretch receptors innervated by?

A

large, myelinated fibres

69
Q

When do pulmonary stretch receptors discharge?

A

in response to distension (larger) of the lung

70
Q

When does the activity of the stretch receptors increase?

A

as the lung volume increases during each inspiration

71
Q

What is the reflex that pulmonary stretch receptors activate?

A

the Hering-Breuer inflation reflex

72
Q

What is the Hering-Breuer Inflation Reflex?

A

a decrease in respiratory frequency due to prolonged expiratory time (if the lungs expand increases, the beginning of the next inspiratory effort will be inhibited)

73
Q

Where is the Hering-Breuer Inflation Reflex noticeable? WHere is it not noticeable?

A

in weak adults unless tidal volume exceeds 1L like in exercises. It is not noticeable in infants and animals

74
Q

Where are the irritant receptors located?

A

between airway epithelial cells in the trachea down the respiratory bronchiloes

75
Q

What are the irritant receptors stimulated by?

A

noxious gases
cigarette smoke
histamine
cold air
dust

76
Q

What are irritant receptors innervated by?

A

myelinated fibres

77
Q

What happens when irritant receptors are stimulated?

A

bronchoconstriction and hyperpnea (increased breathing depth

78
Q

What are irritant receptors important in?

A

in the reflex bronchoconstriction triggered by histamine release during an allergic asthmatic attack

79
Q

Where are the junta-capillary receptors found?

A

In the alveolar wall close to the capillaries

80
Q

What innervates the juxta-capillary receptors?

A

non-myelinated fibres

81
Q

What kind of activity do the juxta-capillary receptors have?

A

short-lasting bursts of activity

82
Q

What are juxta-capillary receptors stimulated by?

A

an increase in pulmonary interstitial fluid (pulmonary congestion and edema)

83
Q

What are the reflexes caused by the juxta-capillary receptors?

A

rapid and shallow respiration, intense stimulation causes apnea

84
Q

What do juxta-capillary receptors play a role in?

A

feelings of dyspnea (difficulty breathing) associated with left heart failure and lung edema or congestion

85
Q

What does minute respiration increase linearly within all individuals?

A

Metabolic rate

86
Q

What happens to minute ventilation when exercise increases?

A

it goes up to 50% - 65% of VO2 max. After there is hyperventilation starting

87
Q

What happens to arterial PO2 when exercise increases?

A

increase in PO2

88
Q

What happens to arterial PCO2 when exercise increases?

A

decrease in PCO2

89
Q

What happens to pH when exercise increases?

A

decrease in pH

90
Q

The role of the central chemoreceptors is important at ___ but not so much during ___. Why?

A

rest
exercise

Because even if exercise causes an increase in arterial pH, H+ doesn’t cross the blood-brain barrier and so can’t be detected by the central chemoreceptors

91
Q

What increases the sensitivity of the peripheral chemoreceptors to CO2 and H+ during exercise?

A

The fluctuations of PaO2

PHGY 210 (10 decks)

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