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Guyton Chapters > Ch42 Regulation of Respiration > Flashcards

Ch42 Regulation of Respiration Flashcards

1
Q

What is the primary function of the nervous system in relation to respiration?

A

Adjusts the rate of alveolar ventilation to meet the body’s demands, maintaining stable PO2 and PCO2 levels

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2
Q

What are the three major collections of neurons in the respiratory center?

A
  • Dorsal respiratory group (inspiration)
  • Ventral respiratory group (expiration)
  • Pneumotaxic center (controls rate and depth of breathing)
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3
Q

Where is the dorsal respiratory group located?

A

In the dorsal portion of the medulla

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4
Q

What is the main role of the dorsal respiratory group of neurons?

A

Causes inspiration and controls respiratory rhythm

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5
Q

What is the significance of the nucleus of the tractus solitarius (NTS) in respiration?

A

It is the sensory termination for vagal and glossopharyngeal nerves transmitting sensory signals into the respiratory center

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6
Q

What happens to the basic rhythm of respiration when peripheral nerves are sectioned?

A

The dorsal respiratory group continues to emit repetitive bursts of inspiratory neuronal action potentials

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7
Q

What is the inspiratory ‘ramp’ signal?

A

A nervous signal that gradually increases over about 2 seconds, then ceases abruptly for expiration

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8
Q

What are the two controlled qualities of the inspiratory ramp signal?

A
  • Rate of increase of the ramp signal
  • Limiting point at which the ramp ceases
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9
Q

True or False: The ventral respiratory group is responsible for the basic rhythmical oscillation of respiration.

A

False

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10
Q

What does the pneumotaxic center control?

A

The ‘switch-off’ point of the inspiratory ramp, thereby controlling the duration of inspiration

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11
Q

How does the strength of the pneumotaxic signal affect respiration?

A

A strong signal can increase breathing rate to 30-40 breaths/min, while a weak signal may reduce it to 3-5 breaths/min

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12
Q

What is the Hering-Breuer inflation reflex?

A

A reflex that stops further inspiration when lungs become overstretched, transmitted through stretch receptors

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13
Q

What triggers the Hering-Breuer reflex in humans?

A

When tidal volume exceeds three times normal (>≈1.5 L/breath)

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14
Q

What is the primary goal of respiration?

A

To maintain proper concentrations of O2, CO2, and H+ in the tissues

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15
Q

What primarily stimulates the respiratory center?

A

Excess CO2 or H+ in the blood

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16
Q

Where is the chemosensitive area located?

A

Beneath the ventral surface of the medulla

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17
Q

What is the primary stimulus for the chemosensitive neurons?

A

H+ concentration

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18
Q

Why does blood CO2 have a more potent effect on chemosensitive neurons than blood H+?

A

CO2 easily crosses the blood-brain barrier, while H+ does not

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19
Q

What happens to the stimulatory effect of CO2 after 1 to 2 days?

A

It declines to about one-fifth the initial effect due to renal adjustments

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20
Q

What role does HCO3− play in the respiratory response to CO2?

A

It binds with H+ to reduce their concentrations, affecting respiratory center activity

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21
Q

What is the indirect effect of CO2 on chemosensitive neurons?

A

CO2 reacts with water to form carbonic acid, dissociating into H+ and HCO3−, which stimulates the neurons.

CO2 has a potent indirect effect on respiratory neurons despite having little direct effect.

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22
Q

How does a change in blood CO2 concentration affect respiratory drive?

A

It has a potent acute effect but only a weak chronic effect after several days of adaptation.

This indicates the body’s ability to acclimate to changes in CO2 levels over time.

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23
Q

What is the normal range of blood PCO2 that significantly increases ventilation?

A

Between 35 and 75 mm Hg.

This range shows the sensitivity of the respiratory system to CO2 changes.

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24
Q

Do changes in O2 concentration have a direct effect on the respiratory center?

A

No, they have virtually no direct effect but can indirectly affect through peripheral chemoreceptors.

Oxygen primarily influences respiration through peripheral chemoreceptors, especially when O2 levels are low.

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25
Where are most chemoreceptors located?
In the carotid bodies and aortic bodies. ## Footnote These chemoreceptors are crucial for detecting changes in blood O2 levels.
26
What happens when arterial oxygen concentration falls below normal?
Chemoreceptors become strongly stimulated, increasing respiratory activity. ## Footnote This effect is particularly sensitive in the range of 60 mm Hg down to 30 mm Hg.
27
What is the role of glomus cells in carotid bodies?
They function as chemoreceptors and synapse with nerve endings to stimulate respiration. ## Footnote Glomus cells detect low O2 levels and trigger neurotransmitter release to activate afferent neurons.
28
How does increased CO2 or H+ concentration affect chemoreceptors?
It excites chemoreceptors and indirectly increases respiratory activity. ## Footnote The direct effects of CO2 and H+ on the respiratory center are significantly more powerful.
29
What is acclimatization in the context of low O2 environments?
The respiratory center loses sensitivity to changes in PCO2 and H+, allowing for greater alveolar ventilation in low O2 conditions. ## Footnote This adaptation can lead to a 400% to 500% increase in ventilation after 2 to 3 days at high altitudes.
30
What is the effect of low arterial PO2 on alveolar ventilation?
Ventilation increases approximately six-fold as PO2 decreases from 100 mm Hg to 20 mm Hg. ## Footnote The effect of hypoxia on ventilation is modest for PO2 values greater than 60 to 80 mm Hg.
31
What happens to arterial PCO2, PO2, and pH during strenuous exercise?
They remain almost exactly normal despite a 20-fold increase in O2 consumption and CO2 formation. ## Footnote This indicates the body's efficiency in regulating respiratory parameters during intense physical activity.
32
What are the effects of PCO2, pH, and PO2 on alveolar ventilation?
They interact to affect ventilation levels, with specific curves representing these relationships. ## Footnote Different pH levels shift the curves, indicating how changes in these factors influence ventilation.
33
What happens to O2 consumption and CO2 formation during strenuous exercise?
They can increase as much as 20-fold.
34
How does alveolar ventilation respond to increased oxygen metabolism during exercise?
It increases almost exactly in step with the increased level of oxygen metabolism.
35
What remains almost exactly normal in a healthy athlete during exercise?
Arterial PO2, PCO2, and pH.
36
What is a predominant cause of increased ventilation during exercise?
Neurogenic signals transmitted to the brain stem respiratory center.
37
True or False: Blood chemical changes are the primary cause of increased respiration during exercise.
False.
38
What happens to ventilation at the onset of exercise?
It increases almost instantaneously.
39
During exercise, how does arterial PCO2 change immediately after the onset of exercise?
It does not increase initially and may actually decrease.
40
What is the role of neurogenic signals during exercise?
They stimulate the respiratory center to match the extra O2 required for exercise and blow off extra CO2.
41
What occurs to CO2 levels as exercise continues after the initial increase in ventilation?
The amount of CO2 released into the blood matches the increased rate of ventilation.
42
What effect does arterial PCO2 have on ventilation when exercising?
It has an extra stimulatory effect at values greater than 40 mm Hg and a depressant effect at values less than 40 mm Hg.
43
What type of receptors are stimulated when pulmonary capillaries become engorged?
J receptors.
44
What can cause respiratory depression due to brain edema?
Acute brain edema from a concussion can depress the respiratory center.
45
How can respiratory depression from brain edema be temporarily relieved?
By intravenous injection of a hypertonic solution like mannitol.
46
What is the most common cause of respiratory depression and arrest?
Overdosage with anesthetics or narcotics.
47
What is Cheyne-Stokes breathing characterized by?
Slowly waxing and waning respiration occurring every 40 to 60 seconds.
48
What happens to blood CO2 and O2 during Cheyne-Stokes breathing?
Overbreathing leads to decreased CO2 and increased O2, followed by a depression of the respiratory center.
49
What are two conditions that can lead to Cheyne-Stokes breathing?
* Long delays in blood transport from the lungs to the brain * Increased negative feedback gain in respiratory control areas.
50
What is obstructive sleep apnea often caused by?
Increased fat deposition in the soft tissues of the pharynx.
51
What are common treatments for obstructive sleep apnea?
* Surgery to remove excess fat tissue * Nasal ventilation with CPAP.
52
What is central sleep apnea characterized by?
Transient abolition of the neural drive to respiratory muscles.
53
What can cause cessation of the ventilatory drive during sleep?
Damage to central respiratory centers or abnormalities of the respiratory neuromuscular apparatus.
54
What type of breathing occurs in patients with damage to the respiratory centers of the brain?
Cheyne-Stokes breathing ## Footnote This type of breathing may indicate severe brain malfunction and can precede death.
55
What physiological changes occur during Cheyne-Stokes breathing?
PCO2 of the pulmonary blood changes in advance of the PCO2 of the respiratory neurons ## Footnote The depth of respiration corresponds with the PCO2 in the brain.
56
In central sleep apnea, what happens to the ventilatory drive?
It transiently ceases ## Footnote This can lead to decreased ventilation even when patients are awake.
57
What are typical causes of central sleep apnea?
Strokes and disorders affecting respiratory centers ## Footnote These disorders reduce responsiveness to CO2 and H+.
58
How many times can episodes of apnea occur in a night for patients with sleep apnea?
300 to 500 times ## Footnote Each episode can last for 10 seconds or longer.
59
What is the primary cause of obstructive sleep apnea?
Blockage of the upper airway ## Footnote This often involves the pharynx.
60
What percentage of sleep apnea cases is attributed to mixed sleep apnea?
Approximately 15% ## Footnote Pure central sleep apnea accounts for less than 1% of cases.
61
What is the world record for voluntary breath-holding duration under normal conditions?
11 minutes and 54 seconds ## Footnote This record does not include hyperventilation with pure oxygen.
62
What can happen when a person hyperventilates or hypoventilates?
Serious derangements in PCO2, pH, and PO2 can occur ## Footnote This can lead to significant health risks.
63
What effects do sedatives or narcotics have on patients with central sleep apnea?
They further reduce responsiveness of the respiratory centers ## Footnote Patients are extremely sensitive to small doses.
64
Fill in the blank: The most common cause of sleep apnea is obstruction of the _______.
upper airway
65
True or False: Cheyne-Stokes breathing is typically associated with healthy brain function.
False ## Footnote It is often a sign of serious brain issues.
66
What typically worsens breathing disorders in patients with central sleep apnea?
Sleep ## Footnote These patients may experience increased episodes of apnea during sleep.
67
What is the effect of CPAP on patients with obstructive sleep apnea?
It is usually necessary for ventilation at night ## Footnote CPAP helps keep airways open.
68
What is the estimated prevalence of pure central sleep apnea?
Less than 1% of sleep apnea cases
69
What is one method that can sometimes help patients with central sleep apnea?
Medications that stimulate the respiratory centers ## Footnote These medications can help improve respiratory drive.

Guyton Chapters (9 decks)

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