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KLowe Anesthesia Physiology 1: Respiratory > Lecture 6: Regulation Of Respiration > Flashcards

Lecture 6: Regulation Of Respiration Flashcards

1
Q

Where is the respiratory center located?

A

Medulla oblongata and pons

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2
Q

Three major respiratory center groups

A
  • Dorsal respiratory
  • Ventral respiratory
  • Pneumotaxic center
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3
Q

Which respiratory group plays the most fundamental role in control of breathing?

A

Dorsal respiratory group

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4
Q

The DRG controls ___ and ___

A

Inspiration and respiratory rhythm

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5
Q

Where is the DRG located?

A

Medulla; most neurons are contained in the nucleus of the tractus solitarius

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6
Q

What two nerves deliver sensory information to DRG?

A
  • Vagus (X)

- Glossopharyngeal (IX)

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7
Q

DRG receives signals from three sources:

A
  • Peripheral chemoreceptors
  • Baroreceptors
  • Lung receptors
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8
Q

The DRG generates the ___

A

Basic rhythm of respiration

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9
Q

What is the inspiratory “RAMP” signal?

A

The motor signal transmitted from the DRG to the diaphragm

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10
Q

The inspiratory ramp signal is NOT…

A

An instantaneous action potential burst

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11
Q

The inspiratory ramp signal begins ___

A

Weakly

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12
Q

The inspiratory ramp signal increases steadily in a…

A

‘Ramp-like’ manner for 2 seconds to cause contraction of the diaphragm (inspiration)

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13
Q

How does the ramp signal allow expiration to occur?

A

The excitatory ramp signal abruptly stops for 3 seconds to allow relaxation of diaphragm (expiration)

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14
Q

How does the ramp signal cause inspiration to occur?

A

Signal begins weakly and increases steadily in a ‘ramp-like’ manner for 2 seconds to cause contraction of diaphragm (inspiration)

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15
Q

What is the advantage of the ramp signal?

A

It causes a steady increase in inspiratory volume

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16
Q

What are two ways that the ramp is controlled?

A
  • Control of the rate of ramp signal increases

- Control of limiting point at which ramp ceases

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17
Q

Ramp signal ___ during activity, lungs ___

A

Increases more rapidly during activity; lungs fill more rapidly

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18
Q

The earlier the ramp ceases, the ___ the inspiration duration

A

Shorter; this also shortens the duration of expiration

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19
Q

The earlier the ramp ceases, the frequency of respiration ___

A

Increases

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20
Q

The pneumotaxic center transmits signals to ___

A

DRG inspiratory area

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21
Q

The pneumotaxic center functions to ___ inspiration phase of breathing cycle and secondarily ___ the rate of breathing

A

Limit inspiration phase of breathing; secondarily increases the rate of breathing

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22
Q

The pneumotaxic center controls the ___ point of the inspiratory point

A

‘Switch-off’ point

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23
Q

The pneumotaxic center ___ entire respiratory cycle

A

Shortens

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24
Q

Strength of inhibitory signal determines the ___ and ___

A

Duration of filling phase and rate of the breathing cycle

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25
Q

When pneumotaxic signal is strong, ___ inspiration phase and ___ rate

A

Shorter inspiration phase (0.5 sec); increased rate (30 to 40 bpm)

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26
Q

When pneumotaxic signal is weak, ___ inspiration phase and ___ rate

A

Longer inspiration phase (5 sec); reduced rate (3 to 5 bpm)

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27
Q

Where is the ventral respiratory group located?

A

In the medulla, anterior and lateral to DRG

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28
Q

VRG stimulation causes ___ as well as ___

A

Expiration as well as inspiration

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29
Q

VRG is important during…

A

High levels of pulmonary ventilation (exercise)

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30
Q

VRG is ___ during normal quiet respiration

A

Inactive; does not appear to participate in basic rhythmic oscillation which controls respiration

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31
Q

VRG contributes to respiratory drive to increase ___

A

Pulmonary ventilation

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32
Q

VRG stimulates ___ to assist in forced exhalation

A

Abdominal muscles

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33
Q

Where is the apneustic center located?

A

In lower pons

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34
Q

What does the apneustic center do?

A
  • Signals the DRG to prevent or slow down the ‘switch-off’ of inspiratory ramp stimuli
  • Lungs become almost completely filled with air with only occasional short expiratory gasps
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35
Q

The apneustic center operates in association with the ___

A

Pneumotaxic center to control the intensity of inspiration

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36
Q

What is the Hering-Breuer Reflex?

A

A protective feedback reflex which limits the over-inflation of lungs

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37
Q

How does the Hering-Breuer Reflex work?

A
  • Stretch receptors are located in muscular portions of bronchi and bronchioles
  • These receptors transmit signals via the vagus nerve (X) to the DRG when lung is overstretched (TV>1.5L)
  • Feedback responses switches off the inspiratory ramp and stops further inflation
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38
Q

The Hering-Breuer Reflex ___ the rate of respiration

A

Increases

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39
Q

What is the ultimate goal of respiration?

A

To maintain proper concentrations of oxygen, carbon dioxide, and hydrogen ions in the tissue

40
Q

Excess ___ or ___ in the blood act directly on the respiratory center to increase strength of both inspiratory and expiratory motor signals

A

Carbon dioxide or hydrogen ions

41
Q

Does oxygen have a direct effect on respiratory centers?

A

No—acts on peripheral chemoreceptors in carotid and aortic bodies

42
Q

What is the chemosensitive area of brainstem?

A

Highly sensitive area on the ventral medulla surface

43
Q

The chemosensitive area is responsive to changes in ___ or ___

A

Blood PCO2 or hydrogen ion concentration

44
Q

Do hydrogen ions easily cross the blood-brain barrier?

A

No

45
Q

Changes in the blood hydrogen ion concentration have ___ effect in stimulating the chemosensitive neurons than changes in blood carbon dioxide

A

Less effect

46
Q

How does CO2 stimulate neurons in the chemosensitive area of the brainstem?

A

By changing the hydrogen ion concentration

47
Q

Respiratory center activity is increased very strongly by elevations in ___

A

Blood carbon dioxide levels

48
Q

CO2 has a ___ effect on the chemosensitive area

A

Potent, direct effect via H+

49
Q

CO2 is ___ permeable to the blood-brain barrier, so blood and brain concentrations of CO2 are ___

A

Highly; equal

50
Q

How does CO2 react with water to affect the chemosensitive area of the brain?

A

CO2 reacts with H2O to form carbonic acid, which dissociates into hydrogen and bicarbonate ions in interstitial fluid of medulla or CSF; release of H+ ions in brain stimulate respiratory center activity

51
Q

Excitation of respiratory center by CO2 is greatest in ___

A

The first hours of carbon dioxide increase

52
Q

After first 1 to 2 days of carbon dioxide exposure, the stimulatory respiration response ___

A

Declines

53
Q

The effect of CO2 on the respiratory response after first 1 to 2 days decreases to about ___ the initial response

A

A fifth of the initial response

54
Q

Why is there a decline in the respiratory response to CO2 after the first 1 to 2 days?

A

The decline results from renal adjustment of hydrogen ion concentration back to normal

55
Q

Changes in blood CO2 concentration has ___ acute effect on controlling respiratory drive but a ___ chronic effect after a few days of adaptation

A

Potent acute effect; weak chronic effect

56
Q

COPD patients have a ___ response to increased CO2

A

Blunted response

57
Q

Increase in PCO2 (above 35 mm Hg) = ___ in ventilation

A

Drastic increase in ventilation

58
Q

Steep part of curve =

A

Blood PCO2 above 35 mm Hg

59
Q

Decreased pH causes a ___ increase in ventilation

A

Smaller increase in ventilation

60
Q

Change in respiration is ___ times less with blood pH range between 7.3 and 7.5

A

10 times less

61
Q

Changes in oxygen have ___ on respiratory center

A

No direct effect

62
Q

Changes in O2 concentration act indirectly on ___

A

Peripheral receptors

63
Q

Hemoglobin-oxygen buffer system delivers normal amounts of O2 to tissues over wide range of pulmonary O2 partial pressures—

A

60 mm Hg to 1000 mm Hg—the large O2 reserve created by this buffer system is the reason why the respiratory center is not affected by oxygen changes as drastically as the respiratory center responds to PCO2 changes

64
Q

Blood oxygen levels below PO2 of ___ are sensed by peripheral chemoreceptors

A

70 mm Hg

65
Q

Chemoreceptors are located in ___ and ___

A

Carotid and aorta

66
Q

What are carotid bodies?

A

Bifurcations in common carotid

67
Q

What type of nerve fibers are in the carotid bodies?

A

Afferent nerve fibers

68
Q

Afferent nerve fibers pass via CN ___ to act on ___

A

IX (glossopharyngeal) to act on DRG

69
Q

Where are the aortic bodies?

A

Aortic arch

70
Q

Innervation of the aortic bodies

A

CN X (vagus) to DRG

71
Q

What O2 range stimulates the chemoreceptors?

A

60 mm Hg to 30 mm Hg (hypoxia)—when hemoglobin-oxygen saturation decreases rapidly

72
Q

Increases in CO2 and hydrogen ion concentration causes…

A

Increase in respiratory activity

73
Q

Direct effect of CO2 and pH is ___ times more powerful

A

7 times

74
Q

Peripheral stimulation occurs ___ times more rapidly

A

5 times

75
Q

Peripheral receptors are important to increase response to CO2 at onset of ___

A

Exercise

76
Q

Ventilatory drive by low blood oxygen content (when CO2 and pH remain normal) is not significant until PO2 falls below ___

A

100 mm Hg

77
Q

Ventilation ___ when PaO2 falls below 60 mm Hg

A

Doubles

78
Q

Acclimatization

A

The idea that oxygen drives the respiratory center in mountain climbers—respiratory center loses most sensitivity to PCO2 and pH changes over 2 to 3 days

79
Q

Alveolar ventilation increases greater than ___ after acclimatization in response to low PaO2

A

400%

80
Q

Alveolar ventilations curves are displaced to the ___ at higher pH

A

Right

81
Q

Alveolar ventilation curves are displaced to the ___ at lower pH

A

Left

82
Q

Strenuous exercise can increase oxygen consumption and carbon dioxide formation by ___

A

20-fold

83
Q

Alveolar ventilation ___ with increased metabolism during exercise

A

Increases (linear relationship)

84
Q

During strenuous exercise, PO2, PCO2, and pH remain ___

A

Almost exactly normal

85
Q

What stimulates respiration during exercise?

A

The PCO2 and PO2 changes caused by exercising muscles

86
Q

Neurogenic factors stimulate respiratory center to supply ___ and ___ removal

A

O2 and CO2 removal

87
Q

Chemical factors provide adjustment in respiratory control to keep ___ and ___ normal

A

CO2 and pH

88
Q

Is voluntary control of respiration mediated through the respiratory center?

A

No—pathway goes from cortex and higher centers downward through corticospinal tract to spinal neurons that drive respiratory muscles

89
Q

What are the “J receptors”?

A

Sensory nerve endings in alveolar walls that juxtapose the pulmonary capillaries

90
Q

The ‘J receptors’ become stimulated when…

A

Engorged by blood or when pulmonary edema occurs, as in CHF

91
Q

How does brain edema affect respiratory center activity?

A

Depresses/inactivates activity (i.e.: head trauma, concussion)

92
Q

Treatment for brain edema

A

Mechanical hyperventilation and hypertonic diuresis

93
Q

What is periodic breathing?

A

Pattern of short intervals of deep breathing follow by periods of shallow or absent breaths—Cheyne-Stokes is most common periodic cycling

94
Q

What causes Cheyne-Stokes breathing?

A

Over-breathing causes a decrease of CO2 and increases blood oxygen in pulmonary blood
Altered pulmonary blood is transported to brain to inhibit excess ventilation
Response is delayed in depressing respiratory center because it takes a few seconds for brain to respond
After a pause in breathing, the cycle resumes with rapid deep breaths again

95
Q

The potential for C-S breathing is present in ___

A

Everyone!

96
Q

Under normal conditions, C-S breathing is ___

A

Highly ‘damped’

97
Q

Two separate conditions that allow C-S breathing to occur:

A
  • Long delay in transport of blood from lungs to brain (low CO)
  • Increased negative feedback gain (brain damage) due to hypoxia or severe metabolic abnormality

KLowe Anesthesia Physiology 1: Respiratory (13 decks)

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