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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 its job

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2
Q

What are the 3 ways respiratory failure can occur?

A
  1. gas exchanging capabilities
  2. neural control of ventilation
  3. neuromuscular breathing apparatus
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3
Q

What is blood hypoxia?

A

deficient blood oxygenation

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4
Q

What are the levels of PaO2 and % Hb saturation in blood hypoxia?

A

low PaO2 and low % Hb saturation

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5
Q

What are the 5 general causes of hypoxia?

A
  1. inhalation of low PO2 (high altitude)
  2. hypoventilation
  3. ventilation imbalance
  4. shunts of blood across the lungs
  5. O2 diffusion impairment
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6
Q

What happens to PaO2 and PaCO2 during hypoventilation?

A

PaO2 decreases and PaCO2 increases

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7
Q

How does hypoventilation happen?

A

due to disease affecting the CNS, neuromuscular diseases, barbiturates and other drugs/narcotics

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8
Q

How does ventilation imbalance in the lungs occur?

A

when the amount of fresh gas reaching an alveolar region per breath is too little for the blood flow through the capillaries of that region

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9
Q

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

A

it bypasses the gas exchange region of the lungs and returns to systemic circulation, deoxygenated

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10
Q

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

A

foramen ovale

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11
Q

What are 2 examples of O2 diffusion impairment?

A

thickening of the alveolar capillary membrane or pulmonary edema

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12
Q

What kind of control is breathing under?

A

voluntary and involuntary control

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13
Q

Which neurological structures control voluntary breathing?

A

the cerebral hemispheres

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14
Q

Which neurological structures control involuntary breathing?

A

the brainstem (pons + medulla)

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15
Q

What happens when you stop ventilation voluntarily?

A

breathing will eventually start again

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16
Q

What is the breaking point?

A

when arterial PCO2 and PO2 has reached levels where voluntary control is over-ridden

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17
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

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18
Q

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

A

sensors, controllers and effectors

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19
Q

What is the function of sensors?

A

they gather information about lung volume and O2/CO2 content

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20
Q

What are the two kinds of sensors?

A

pulmonary receptors and chemoreceptors

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21
Q

How is information sent to controllers?

A

via afferent neural fibres

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22
Q

Where are controllers located?

A

in the pons and medulla

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23
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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24
Q

What is another name for effectors?

A

the respiratory muscles

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25
Q

Why are neuronal impulses sent to effectors?

A

so that ventilation can be adjusted to the person’s metabolic needs

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26
Q

Where are the pacemakers cells located?

A

the ventral respiratory group of the medulla

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27
Q

What is the function of the ventral respiratory group?

A

they generate the basic rhythm

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28
Q

What does the ventral respiratory group contain?

A

pre-Botzinger complex

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29
Q

What is the function of the dorsal respiratory group?

A

they receive several sensory inputs

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30
Q

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

A

inspiratory motor neurons

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31
Q

What kind of rhythmicity do the respiratory neurons in the medulla generate?

A

the basic respiratory rhythmicity

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32
Q

What kind of cells are found in the medulla?

A

pacemaker cells

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33
Q

What is another name for the upper pons?

A

the pneumotaxic centre

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34
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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35
Q

Does the upper pons turn on or turn off inspiration?

A

turn off

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36
Q

What happens to the tidal volume and breathing frequency when the upper pons turns off inspiration?

A

tidal volume: becomes smaller
breathing frequency: increases

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37
Q

What happens to breathing when the pneumotaxic centres are cut?

A

it becomes deep and slow

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38
Q

What happens to breathing when the vagus nerves are cut?

A

it becomes deep and slow

39
Q

What is another name for the lower pons?

A

the apneustic centre

40
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

41
Q

What does the lower pons promote?

A

inspiration

42
Q

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

A

apneuses

43
Q

What kind of breathing is seen in some severe types of brain injury?

A

apneuses

44
Q

What is apneuses?

A

tonic inspiratory activity interrupted by short expirations

45
Q

What do chemoreceptors detect?

A

PO2, PCO2 and pH in arterial blood

46
Q

Where is information from the chemoreceptors carried to?

A

to the respiratory neurons

47
Q

When will the activity of respiratory neurons increase?

A
  • PaO2 <60mmHg
  • PaCO2 >40 mmHg
48
Q

When will the activity of respiratory neurons decrease?

A
  • PaO2 > 100 mmHg
  • PaCO2 < 40 mmHg
49
Q

What are the two kinds of chemoreceptors?

A

central and peripheral

50
Q

Where are central chemoreceptors located?

A

on the ventral surface of the medulla

51
Q

What do the central chemoreceptors detect?

A

the pH of the cerebrospinal fluid surrounding them

52
Q

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

A

the PCO2 of the arterial blood

53
Q

What do the central chemoreceptors give rise to?

A

the main drive to breathe under normal conditions

54
Q

How can the sensitivity of central chemoreceptors be assessed?

A

by a CO2 rebreathing test

55
Q

What happens during a CO2 rebreathing test?

A

a subject breathes different CO2 mixtures or rebreathes expired air from a bag filled with O2 so that with each expiration, the inspired PCO2 gradually increases

56
Q

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

A

minute ventilation increases, hyperventilation, decrease in PCO2 in the blood and CSF

57
Q

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

A

linear

58
Q

What are peripheral chemoreceptors mainly sensitive to?

A

changes in PO2

59
Q

What are peripheral chemoreceptors stimulated by?

A

increased PCO2 and decreased pH

60
Q

Where are peripheral chemoreceptors located?

A

in carotid bodies (the bifurcation of the common carotid arteries) and in the aortic bodies (next to the ascending aorta)

61
Q

What are the carotid and aortic bodies made up of?

A

blood vessels, structural supporting tissue and nerve endings of sensory neurons of the glossopharyngeal and vagus nerve

62
Q

What two nerves make up the carotid and aortic bodies?

A

the glossopharyngeal and vagus nerves

63
Q

Where do the afferent fibers of the peripheral chemoreceptors projected?

A

to the dorsal group of the respiratory neurons in the medulla

64
Q

How can the sensitivity of peripheral chemoreceptors be assessed?

A

by having a subject breathe gas mixtures with decreased concentrations of O2

65
Q

What pressure does O2 have to be in order to have an appreciable change in minute ventilation?

A

60 mmHg

66
Q

At increased PCO2, a decrease of PO2 below ___ can already cause an increase in minute ventilation.

A

100 mmHg

67
Q

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

A

increase, decrease

68
Q

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

A
  1. pulmonary stretch receptors
  2. irritant receptos
  3. j receptors
69
Q

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

A

in the vagus nerves

70
Q

Where are pulmonary stretch receptors located?

A

in smooth muscles of the trachea down to the terminal bronchioles

71
Q

What are pulmonary stretch receptors innervated by?

A

large, myelinated fibres

72
Q

When do pulmonary stretch receptors discharge?

A

in response to distension of the lung

73
Q

When does the activity of the stretch receptors increase?

A

as lung volume increases during each inspiration

74
Q

What is the reflex that stimulates pulmonary stretch receptors?

A

the Hering-Breuer Inflation Reflex

75
Q

What is the Hering-Breuer Inflation Reflex?

A

a decrease in respiratory frequency due to a prolongation of expiratory time

76
Q

Where is Hering-Breuer Inflation Reflex noticeable?

A

in infant and animals

77
Q

Where are the irritant receptors located?

A

between airway epithelial cells in the trachea down to the respiratory bronchioles

78
Q

What are the irritant receptors stimulated by?

A

noxious gases, cigarette smoke, histamine, cold air and dust

79
Q

What are irritant receptors innervated by?

A

myelinated fibers

80
Q

What happens when irritant receptors are stimulated?

A

bronchoconstriction and hyperpnea happens

81
Q

What are irritant receptors important in?

A

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

82
Q

Where are the junta-capillary receptors found?

A

in the alveolar walls close to the capillaries

83
Q

What innervates the juxta-capillary receptors?

A

non-myelinated fibres

84
Q

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

A

short lasting bursts

85
Q

What are juxta-capillary receptors stimulated by?

A

an increase in pulmonary interstitial fluid

86
Q

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

A

rapid and shallow respiration and apnea

87
Q

What do juxta-capillary receptors play a role in?

A

dyspnea associated with left heart failure and lung edema or congestion

88
Q

What does minute ventilation increase linearly with?

A

VO2

89
Q

What happens to minute ventilation when exercise increases?

A

it increases

90
Q

What happens to arterial PO2 when exercise increases?

A

it remains constant

91
Q

What happens to arterial PCO2 when exercise increases?

A

it stays constant then decreases

92
Q

What happens to pH when exercise increases?

A

it increases

93
Q

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

A

rest, exercise

94
Q

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

A

fluctuations in PaO2

PHGY-210 (36 decks)

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