7 Control & Ventilation Flashcards

1
Q

Why is Ventilatory control reliant on signalling from the brain?

A

Diaphragm and intercostal muscles are skeletal muscle
Stimulated by alpha-motor neurons to act unlike smooth/cardiac

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2
Q

What innervates the diaphragm?

A

Phrenic nerve

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3
Q

Where does the phrenic nerve origniate?

A

C3, C4, C5

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4
Q

Where are the respiratory centres found?

A

Pons and medulla

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5
Q

What are the respiratory centres in the medulla called?

A

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

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6
Q

How do respiratory centres set an automatic breathing rhythm?

A

Co-ordinating & firing smooth and repetitive bursts of APs in DRG.

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7
Q

Where does the DRG output go?

A

Mainly to inspiratory muscles

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8
Q

Why does the DRG still fire during expiration?

A

Gives slow controlled expiration

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9
Q

Where does the VRG output go?

A

Inspiratory muscles
Pharynx muscle
Larynx muscle
Tongue muscles

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10
Q

Why does the VRG also fire during expiration?

A

Maintain patency of the airway

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11
Q

Which cranial nerves enter the respiratory centres?

A

Cranial Nerve 9 & 10 bring mechanical and chemosensory data

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12
Q

What 4 things can modulate rhythm?

A
  • Emotion via limbic system
  • Voluntary over ride from higher brain centres
  • Mechano-Sensory input from thoracic wall
  • Chemical composition of blood (PCO2, PO2, pH)
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13
Q

Whats the use of mechano-sensory input from the thoracic wall?

A

Safety mechanism preventing over inflation (i.e. stretch reflex)

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14
Q

Which input has the largest effect on breathing rhythm?

A

Chemoreceptors, i.e. chemical composition of blood

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15
Q

What do central chemoreceptors respond to?

A

[H+] changes in CSF around brain which reflect PCO2 levels
Primary drive for ventilation

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16
Q

Where are central chemoreceptors found?

A

Medulla

17
Q

Where are peripheral chemoreceptors found?

A

Carotid & Aortic Bodies

18
Q

Where are carotid bodies found?

A

Neck where carotid divides into internal/external artery

19
Q

Where are aortic bodies found?

A

Aortic arch

20
Q

What do peripheral chemoreceptors respond to?

A

[H+] in plasma & PO2

21
Q

Why do central chemoreceptors only detect H+ reflecting CO2 levels?

A

H+ cant cross blood brain barrier
CO2 can cross
CO2 forms carbonic acid which dissociates into H+ in CSF

22
Q

What is a raised PCO2 called?

A

Hyercapnia

23
Q

How does the body respond to hypercapnia?

A

Reflex ventilation

24
Q

When does a raised PCO2 often occur?

A

During hypoventilation