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_Physiology Exam 4 > 4/1: Control of Respiration > Flashcards

4/1: Control of Respiration Flashcards

1
Q

What does high levels of CO2 or H+ activate?

A

activates respiratory centers to increase alveolar ventilation (AV = (TV – DS) x RR)

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2
Q

What is a more sensitive regulator for alveolar ventilation?

A

CO2 (small changes in CO2 causes spike in alveolar ventilation)

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3
Q

What are CO2 or H levels detected by?

A

both peripheral (arteries) and central (medulla) chemoreceptors

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4
Q

What do low levels of O2 increase?

A

Alveolar ventilation

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5
Q

What is not a sensitive regulator?

A

O2 levels have to drop significantly to cause
spike in alveolar ventilation

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6
Q

What does not directly impact central respiratory centers?

A

Increases in alveolar ventilation
instead acts on peripheral chemoreceptors (in arteries) that relay the signal to the
central respiratory center

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7
Q

What are the two basic controls of breathing?

A

Voluntary
Automatic

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8
Q

What tract controls the voluntary control of breathing?

A

Corticospinal tract

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9
Q

What does the corticospinal tract involve?

A

descending input from thalamus and cerebral cortex, can bypass the respiratory control centers in pons and medulla

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10
Q

What is the voluntary control of breathing activated by?

A

talking, sneezing, singing, swallowing, coughing, defecation, anxiety, fear, etc

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11
Q

What tract controls the atomatic control of breathing?

A

Ventrolateral tract

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12
Q

What is the automatic control of breathing controlled by?

A

Changes in PCO2
- less sensitive to PO2 and H
- pulmonary mechanical receptors

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13
Q

What is the automatic control activated by?

A

Respiratory centers in the pons and medulla (DRG and VRG)

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14
Q

What are the two medullary respiratory centers?

A

Dorsal respiratory group (DRG)
Ventral respiratory group (VRG)

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15
Q

What does the dorsal respiratory group initiate?

A

Inspiration

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16
Q

What does the ventral respiratory group initiate?

A

Active expiration and greater than normal inspiration

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17
Q

What are the two centers involved in pontine respiratory group?

A

Pneumotaxic center
Apneustic center

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18
Q

What is the nucleus for the dorsal respiratory group?

A

Tractus solitarius (NTS)

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19
Q

What is the inspiratory center?

A

Dorsal respiratory group

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20
Q

What does the DRG receive afferent input from?

A

CN IX (chemoreceptor) and X (chemoreceptor and mechanoreceptor)

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21
Q

What stimuli does the DRG provide?

A

Excitatory inspiratory stimuli to phrenic motor neurons

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22
Q

What generator does a DRG have?

A

Central pattern generator
- sets the basic rhythm for breathing by setting the frequency of inspiration

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23
Q

What activity does the DRG mirror?

A

Diaphragm (contraction needed for inspiration.
Releases Ach onto nicotinic)

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24
Q

What do opiate receptors do when activated?

A

(contained in DRG) when activated, inhibit respiration and decrease sensitivity to changes in PCO2

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25
Q

What nuclei are involved in ventral respiratory group (VRG)?

A

Nucleus amiguus and nucleus retroambiguus

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26
Q

What is the VRG primarily responsible for?

A

Expiration
- Expiration is normally a passive process so these
neurons are quiescent during normal breathing, but activated when forceful
expiration is required

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27
Q

What does the VRG control motor neurons for?

A

▪ Expiratory muscles (internal intercostals and abdominals)
▪ Accessory inspiratory muscles (when you want to increase tidal volume)
▪ Pre-Bontzinger complex: have respiratory pacemaker control

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28
Q

What does the afferent (sensory) information regulate?

A

the activity of the medullary inspiratory center (DRG) via central and peripheral chemoreceptors and also mechanoreceptors (lung stretch and muscle/joint receptors)

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29
Q

Where are peripheral chemoreceptors located?

A

Arterial (located in the aortic, CN X, and carotid, CN IX, bodies)

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30
Q

What do peripheral chemoreceptors respond to?

A

Respond low O2, higher than normal CO2, and higher than normal H+

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31
Q

What are the only receptors that are sensitive to oxygen?

A

Peripheral chemoreceptors

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32
Q

Where are central chemoreceptors located?

A

Medullary (located on ventral surface of medulla)

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33
Q

What do central chemoreceptors respond to?

A

Only respond to higher than normal H+ levels (which occurs with high CO2)

34
Q

What are central chemoreceptors very sensitive to?

A

Changes in CSF pH

35
Q

What are herin-breuer reflexes used to achieve?

A

Optimal rate and depth

36
Q

When are stretch receptors in bronchi and bronchioles activated?

A

when the lungs over-stretch. To activate this reflex, tidal volume must increase > 3 times (~1.5L/breath)

37
Q

What is the result of hering-breuer reflex?

A

Stops further inspiration and decreases rate

38
Q

What is the function of irritant receptors?

A

Protection

39
Q

Where are irritant receptors located?

A

Between epithelial cells in conducting zone

40
Q

What are irritant receptors stimulated by?

A

Noxious exogenous substances, endogenous agents, and mechanical stimulation

41
Q

What do irritant receptors promote?

A

Rapid, shallow breathing, coughing, sneezing, etc

42
Q

What is the function of J receptors?

A

Unclear

43
Q

Where are J receptors found?

A

Alveolar walls, “juxtacapillary”

44
Q

What are J receptors stimulated by?

A

Alveolar inflammatory processes (pneumonia), pulmonary vascular congestion (congestive heart failure), and edema

45
Q

What do J receptors cause?

A

Rapid, shallow breathing and a sensation of dyspnea

46
Q

What are joint and muscle proprioceptors sensitive to?

A

change in position and muscle movements—not metabolism

47
Q

What do joint and muscle proprioceptors do?

A

Increase activity of DRG to increase rate of breathing

48
Q

What movements in joint and muscle proprioceptors stimulate respiration?

A

Active and passive

49
Q

What are the purpose of joint and muscle proprioceptors?

A

send stimulatory impulses to the medullary centers, increasing inspiratory activity and hyperpnea

50
Q

What does moving the limbs, slapping the skin, and other painful stimuli (also splashing cold water) stimulate?

A

ventilation in patients who have respiratory depression

51
Q

Proprioceptors in joints and tendons may be important in initiating and maintaining…

A

increased ventilation at the beginning of exercise

52
Q

Inspiratory muscle force automatically adjusts to?

A

the load imposed by decreased lung compliance or increased airway resistance

53
Q

What are central chemoreceptors most important for?

A

minute-to-minute control of breathing (most effective for 1-2 days)

54
Q

Where are central chemoreceptors located?

A

Ventral surface of medulla

55
Q

What does activation of central chemoreceptors stimulate?

A

The DRG

56
Q

What are central chemoreceptors sensitive to?

A

Changes in pH of CSF

57
Q

What is a drop in CSF pH reflective of?

A

(only) a higher than normal amount of PCO2

58
Q

What are chemoreceptors in the CSF only sensitive to?

A

Changes in H+ concentration

59
Q

What happens to respiratory volume and rate when CSF (H+) increases?

A

increase in respiratory volume and rate

60
Q

Describe the activation of central chemoreceptors by CSF

A
  1. CO2 is permeable to the Blood Brain Barrier
  2. In the CSF, CO2 is converted to H+ and HCO3- via Carbonic Anhydrase
  3. The H+ produced in the CSF activates the Central Chemoreceptors which stimulates the DRG
61
Q

What is sample arterial blood sensitive to (activated by)?

A

Low PaO2, High PaCO2, and Low pH
**only sensitive to dissolved gases

61
Q

When are central chemoreceptors most effective for?

A

Within 1-2 days after a change in central CO2

62
Q

Why are central chemoreceptors most effective within 1-2 days?

A

This is because during (& after) that time period
– the kidneys will have begun to compensate, reabsorbing
HCO3-
– HCO3- has slowly diffused through the BBB and CSF barriers to buffer H+

62
Q

What is a danger for patients with chronic respiratory problems?

A

the kidney and buffer mechanisms compensate for the elevated PaCO2 (and H+) so that they no longer stimulate the medullary respiratory centers

63
Q

What becomes critical for respiratory control in patients with chronic respiratory problems?

A

the peripheral chemoreceptors-the only receptors that sample oxygen content

64
Q

What nerve forms the carotid bodies?

A

Glossopharyngeal nerves (CN IX)

64
Q

What nerve forms the aortic bodies?

A

Vagus nerves (CN X)

65
Q

Where are peripheral chemoreceptors located?

A

In the aortic bodies and carotid bodies

66
Q

What does a decrease of oxygen in peripheral chemoreceptors cause?

A

Increase in rate of firing
- Have to fall to below 60 to
see large increase in alveolar ventilation (AV)
▪ Due to hemoglobin saturation decrease (you want increase in AV if Hb
saturation decreases)

67
Q

What does an increase in CO2 levels in peripheral chemoreceptors cause an increase in?

A

the rate of firing of both aortic
and carotid bodies to increase respiration
**Not as powerful as central changes in response to PaCO2 but respond 5x
more quickly

68
Q

What does a PaCO2 greater than 35 mmHG stimulate?

A

an increase in alveolar respiration

69
Q

What happens if blood O2 is low and CO2 is high?

A

the peripheral chemoreceptors have a bigger response than they would if just one of them was increased/decreased

70
Q

What enhances the response to PaCO2?

A

Hypoxemia

71
Q

What does a decrease in arterial pH cause?

A

Increasein the rate or carotid bodies
▪ Takes a greater change in pH to stimulate an increase in alveolar ventilation
▪ Independent of CO2 change

72
Q

What cause enhanced responses to PaCO2?

A

(increased H+, enhances response to CO2 and greater AV)
- metabolic acidosis (ketoacidosis)

73
Q

What causes a decreased response to PaCO2?

A

(blunt response to high CO2)
-Sleep
-Opioids/narcotics, chronic obstruction
-Deep anesthesia

74
Q

What do most inhaled anesthetics cause?

A

Respiratory depression

75
Q

How is respiratory depression caused?

A

by inhibiting the DRG and abolish/attenuate the response to hypoxemia (êO2) and hypercarbiaéCO2)

76
Q

What does nitrous oxide (NO2) do to respiratory rate and tidal volume?

A

nitrous oxide increases respiratory rate and
decreases tidal volume so there is minimal change in minute ventilation and
PaCO2 levels

77
Q

What does NO2 do to hypoxic drive?

A

Decreases hypoxic drive

78
Q

What does nitrous oxide do to pulmonary vascular resistance?

A

Increases

79
Q

NO2 is a mild ___________

A

sympathomimetic (activates sympathetic nervous
system)

_Physiology Exam 4 (8 decks)

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