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 repiratory pacemaker cells located?

A

the ventral respiratory group of the medulla

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25
What is the function of the ventral respiratory group of the medulla?
To generate the basic rhythm of breathing
26
What does the ventral respiratory group contain?
pacemaker cells
27
What is the function of the dorsal respiratory group?
it receives several sensory inputs
28
What do the cells in the ventral and dorsal respiratory group connect to?
inspiratory motor neurons
29
What kind of cells are found in the medulla?
pacemaker cells
30
What does the medulla do? how is it affected in the absence of the vagus nerve?
It generates the basic respiratory rhythmicity. Without the vagus nerve, the rhythmicity is the same but with no control of the lung volume
31
What is the function of the upper pons?
it modifies the inspiratory activity of the centres in the medulla
32
Does the upper pons turn on or turn off inspiration?
turn off
33
What happens to the tidal volume and breathing frequency when the upper pons turn off inspiration (when the upper pons are functioning)?
tidal volume: becomes smaller breathing frequency: increases
34
What happens to breathing when the upper pons are cut?
Breathing becomes slow and deep (no more inhibition of inspiration)
35
What happens to breathing when the vagus nerves are cut on an intact brainstem?
It has the same effect as removing the upper pons meaning that breathing will be slow and deep
36
What s the function of the cells located in the lower pons?
They send excitatory impulses to the respiratory groups of the medulla
37
What does the lower pons promote?
They promote inspiration
38
What happens when you remove the upper pons and the vagus nerve?
It causes apneuses, seen in some severe types of brain injuries
39
What is apneuses?
tonic inspiratory activity interrupted by short expirations --> prolonged inspiratory phase followed by an irregular and inadequate expiration
40
What do chemoreceptors detect?
PO2, PCO2 and pH in arterial blood
41
Where is information from the chemoreceptors carried to?
the respiratory neurons
42
At what levels of O2 and CO2 will the activity of respiratory neurons increase?
if PaO2 is lower than 60 mmHg if PaCO2 is greater than 40 mmHg
43
When will the activity of respiratory neurons decrease?
if PaO2 is greater than 100 mmHg if PaCO2 is lower than 40 mmHg
44
What are the two kinds of chemoreceptors?
Central chemoreceptors and Peripheral chemoreceptors
45
Where are central chemoreceptors located?
in the ventral surface of the medulla
46
What do the central chemoreceptors detect?
the pH of CSF
47
What is the pH and PCO2 of the CSF surrounding the central chemoreceptors influenced by?
by the pH and PCO2 of the arterial blood
48
What do the central chemoreceptors give rise to?
the main drive to breathe under normal conditions
49
How can the sensitivity of central chemoreceptors be assessed?
with a CO2 rebreathing test
50
What happens during a CO2 rebreathing test?
Breathing different mixtures of CO2 or rebreathing expired from a bag filled with O2
51
What happens when the chemoreceptors are stimulated during the CO2 rebreathing test?
When the pH of the CSF is reduced due to increased CO2, the chemoreceptors are stimulated to increase ventilation
52
What kind of relationship is there between ventilation and PCO2 in central chemoreceptors?
it is a linear relationship where minute ventilation will increase as soon as PaCO2 increases
53
From the variables responsible for minute ventilation (Ve=Tv x frequency), which is responsible for increased minute ventilation when PCO2 is elevated?
The tidal volume and the frequency increases
54
How do the central chemoreceptors work?
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
What are peripheral chemoreceptors mainly sensitive to?
changes in PO2
56
What are peripheral chemoreceptors secondarily stimulated by?
increases PCO2 and decreased pH
57
Where are peripheral chemoreceptors located?
in the carotid bodies and the aortic bodies
58
What are the carotid and aortic bodies made up of?
blood vessels structural supporting tissue and nerve ending of sensory neurons
59
What two nerves make up the carotid and aortic bodies?
Carotid: glossopharyngeal nerve (IX) Aortic: vagus nerve (X)
60
Where do the afferent fibers of the peripheral chemoreceptors projected?
the the dorsal group of the respiratory neuron in the medulla
61
How can the sensitivity of peripheral chemoreceptors be assessed?
by having subjects breathe gas mixtures with decreased concentrations of O2
62
What pressure does O2 have to be to have an appreciable change in minute ventilation when PCO2 is not increased?
60 mmHg
63
Increasing PCO2, ___ ventilation at ___
increases any PO2
64
An ___ in PCO2 and a ___ in PO2 interact giving an augmented ventilatory response
increase decrease
65
What are the 3 kinds of receptors in the lungs that respond to mechanical stimuli?
Pulmonary stretch receptors Irritant receptors Juxta-capillary receptors (J receptors)
66
Where do the afferent fibres of the receptors that respond to mechanical stimuli travel?
in the vagus nerve
67
Where are pulmonary stretch receptors located?
in the smooth muscle of the trachea down to the terminal bronchioles
68
What are pulmonary stretch receptors innervated by?
large, myelinated fibres
69
When do pulmonary stretch receptors discharge?
in response to distension (larger) of the lung
70
When does the activity of the stretch receptors increase?
as the lung volume increases during each inspiration
71
What is the reflex that pulmonary stretch receptors activate?
the Hering-Breuer inflation reflex
72
What is the Hering-Breuer Inflation Reflex?
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
Where is the Hering-Breuer Inflation Reflex noticeable? WHere is it not noticeable?
in weak adults unless tidal volume exceeds 1L like in exercises. It is not noticeable in infants and animals
74
Where are the irritant receptors located?
between airway epithelial cells in the trachea down the respiratory bronchiloes
75
What are the irritant receptors stimulated by?
noxious gases cigarette smoke histamine cold air dust
76
What are irritant receptors innervated by?
myelinated fibres
77
What happens when irritant receptors are stimulated?
bronchoconstriction and hyperpnea (increased breathing depth
78
What are irritant receptors important in?
in the reflex bronchoconstriction triggered by histamine release during an allergic asthmatic attack
79
Where are the junta-capillary receptors found?
In the alveolar wall close to the capillaries
80
What innervates the juxta-capillary receptors?
non-myelinated fibres
81
What kind of activity do the juxta-capillary receptors have?
short-lasting bursts of activity
82
What are juxta-capillary receptors stimulated by?
an increase in pulmonary interstitial fluid (pulmonary congestion and edema)
83
What are the reflexes caused by the juxta-capillary receptors?
rapid and shallow respiration, intense stimulation causes apnea
84
What do juxta-capillary receptors play a role in?
feelings of dyspnea (difficulty breathing) associated with left heart failure and lung edema or congestion
85
What does minute respiration increase linearly within all individuals?
Metabolic rate
86
What happens to minute ventilation when exercise increases?
it goes up to 50% - 65% of VO2 max. After there is hyperventilation starting
87
What happens to arterial PO2 when exercise increases?
increase in PO2
88
What happens to arterial PCO2 when exercise increases?
decrease in PCO2
89
What happens to pH when exercise increases?
decrease in pH
90
The role of the central chemoreceptors is important at ___ but not so much during ___. Why?
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 A modification in the enviromnment will cause the receptors to react (high CO2 air)
91
What increases the sensitivity of the peripheral chemoreceptors to CO2 and H+ during exercise?
The fluctuations of PaO2