Drive to breathe Flashcards

1
Q

What does the dorsal respiratory group do (DRG)? (2)

A
Normal breathing
Inspiratory neurons (to diaphragm and ext. intercostals)
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2
Q

What does the ventral respiratory group do (VRG)? (3)

A

Forced breathing (e.g. exercise)
Inspiratory & EXPIRATORY neurons
pre-Botzinger complex

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3
Q

What is the pre-Botzinger complex and where is it located?

A

Respiratory rhythm generator –> sets basal respiratory rate

Located in VRG

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4
Q

What does the apneustic centre do? (2)

A

Stimulates DRG

Increases intensity of inhalation (deep breaths)

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5
Q

What does the pneumotaxic centre do? (3)

A

Inhibits apneustic centre
Promotes expiration
Shallow, frequent breaths (to prevent hyperventilation)

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6
Q

What inhibits the apneustic centre?

A

Pneumotaxic centre

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7
Q

Where are the DRG and VRG located?

A

Medulla

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8
Q

Where are the apneustic and pneumotaxic centres located?

A

Pons

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9
Q

What are slowly adapting stretch receptors (SASRs) activated by?

A

Lung distension

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10
Q

During high activity, what do SASRS do?

A

Inhibit further inspiration to begin expiration

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11
Q

What happens to SASRs if lung inflation is maintained?

A

They slowly adapt to low-frequency firing

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12
Q

What are rapidly adapting stretch receptors (RASRs) activated by?

A

Lung distention and irritants

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13
Q

During high activity, what do RASRs cause?

A

Bronchoconstriction

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14
Q

Characteristic of RASR’s response to stimulation?

A

Produce brief burst of activity

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15
Q

What are C fibres J receptors activated by?

A

Increase in interstitial fluid and thus pressure

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16
Q

What do C fibres J receptors do? (4)

A

Rapid, shallow breaths
Bronchoconstriction
CV depression
Dry cough

17
Q

Where are peripheral chemoreceptors located?

A

Carotid bodies

Aortic bodies

18
Q

What do peripheral chemoreceptors respond to?

A

Decreased PaO2

Increased arterial [H+] due to increased CO2

19
Q

How do peripheral chemoreceptors respond on detection of hypoxia? (2)

A

Stimulate medullary inspiratory neurons

Increases ventilation

20
Q

Why aren’t peripheral chemoreceptors sensitive to small reductions of PaO2?

A

Begin firing when PaO2 is near 60mmHg as Hb is 90% saturated.
Increasing ventilation before this would have little increase in PaO2

21
Q

Why is there no peripheral chemoreceptor input in presence of CO?

A

PaO2 is unaffected

CO doesn’t affect amount of O2 dissolved in blood or oxygen-diffusion capacity of the lung

22
Q

Where are central chemoreceptors located?

A

Medulla oblongata

23
Q

What do central chemoreceptors respond to?

A

Increased [H+] of CSF

Very small increases in PaCO2

24
Q

How do central chemoreceptors respond to small increases in PaCO2? (2)

A

Stimulate medullary inspiratory neurons

Increases ventilation

25
Q

Why are central chemoreceptors more sensitive to small increases in PaCO2?

A

CO2 diffuses into CSF and contributes to CSF pH

26
Q

Why are changes in blood [H+] poorly reflected in the CSF?

A

BBB impermeable to H+

27
Q

What causes the drive to breathe?

A

Increased CO2 in blood, not necessarily the low O2

28
Q

What is hypoxia?

A

Deficiency of O2 at tissue level

29
Q

What the 4 common causes of hypoxia?

A
  • Hypoventilation
  • Diffusion impairment
  • Shunting
  • Ventilation-perfusion mismatch (most common cause)
30
Q

What is hypercapnia?

A

CO2 retention and increased PaCO2

Main drive to breathe!

31
Q

What happens in type 1 respiratory failure?

A

1 change: low pO2, normal/low PaCO2

32
Q

What happens in type 2 respiratory failure?

A

2 changes: low pO2, high PaCO2