Control of ventilation Flashcards

1
Q

How are skeletal muscles stimulated during inspiration?

A

Phrenic nerve to diaphragm

Intercostal nerves to external intercostal muscles

Entirely dependant on signalling from the brain

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2
Q

What part of the brain is responsible for ventilatory control?

A

Il defined centres located in the pons and the medulla (respiratory centres)

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3
Q

What is the activity of respiratory centres?

A

Fire repetitive short bursts of action potentials in DRG which travel to the inspiratory muscles

This sets an autonomic rhythm of breathing

They adjust their rhythm according to the stimuli

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4
Q

What does DRG stand for?

A

Dorsal respiratory group

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5
Q

What does PRG stand for?

A

Pontine respiratory group - pneumotaxic area

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6
Q

What does VRG stand for?

A

Ventral respiratory group

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7
Q

What does NTS stand for?

A

Nucleus tractis soolitaris

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8
Q

Which respiratory centre is located in the pons?

A

PRG

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9
Q

What modulates rhythm of respiratory centres?

A
  • Emotion (limbic system of brain)
  • Voluntary over-ride (higher centres in the brain)
  • Mechano-sensory input from the thorax (stretch reflex)
  • Chemical composition of the blood (PCO2, PO2 and pH) – detected by chemoreceptors.
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10
Q

What does the VRG supply?

A

Tongue, pharnyx, larynx, expiratory muscles

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11
Q

What does the DRG supply?

A

Inspiratory muscles via phrenic nerve and intercostal nerve.

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12
Q

What is the most significant input?

A

Chemoreceptor input

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13
Q

What are your central chemoreceptors?

A

Medulla

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14
Q

What chemical change does the medulla detect from the CSF?

A

Responds directly to H+, which directly reflects PCO2

Primary ventilatory drive

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15
Q

What are your peripheral chemoreceptors?

A

Carotid and aortic bodies

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16
Q

What chemical change do the peripheral chemoreceptors detect?

A

Primarily to plasma [H+] and PO2 (not oxygen content) (less so to PCO2)

Second ventilatory drive

17
Q

What is hypercapnea?

A

Raised PCO2

18
Q

What change in blood PCO2 does hyperventilation cause

A

Reduces PCO2 - reduces CSF H+

Inhibits ventilation

19
Q

does the medulla respond to direct changes in the plasma H+?

A

No

20
Q

What crosses the blood brain barrier, PCO2 or H+?

A

PCO2

21
Q

What do the peripheral chemoreceptors cause?

A

Reflex stimulation of ventilation, following a SIGNIFICANT fall in arterial PO2 or rise in H+

22
Q

Dissociation of CO2 in water is - CO2 + H2O H2CO3 HCO3- + H+
Which direction does increased ventilation shift the equilibrium?

A

Increased ventilation drives this equation to the left (by blowing off CO2) and lowers [H+]

Decreased ventilation drives this equation to the right (by retaining CO2) and increases [H+]

23
Q

Which type of chemoreceptors afferent sensory neurones?

A

Carotid and aortic chemoreceptors

24
Q

who is ‘da bomb’?

A

Kitty don O’Leary

25
Q

What do the somatic motor neurones for inspiration and expiration innervate?

A

Inspiration - Scalene and sternocleidomastoid muscles, external intercostals, diaphragm

Expiration - Internal intercostals
Abdominal muscles

26
Q

What allows us to have a large degree of voluntary control over breathing

A

Descending neural pathways from cerebral cortex to respiratory motor neurones..

27
Q

Can cerebral coretex neural pathways override involuntary stimuli such as PCO2 or H+?

A

NO

28
Q

What are examples of voluntary control of ventilation?

A

Breath-holding

Hyperventilation

29
Q

What is the neurotransmitter that responds to low PO2 in the peripheral chemoreceptors?

A

DOPAMINE

30
Q

What type of drugs repress respiratory centre?

A

Barbituates and opiods

31
Q

What is the effect of anaesthetic agents?

A

Increases respiratory rate but decrease Tidal volume so decrease AV.

32
Q

What is the effect of nitrous oxide?

A

Sedative/light anaesthetic agent

Blunts peripheral chemoreceptor response to falling PaO2.

33
Q

When is nitrous oxide problematic?

A

Chronic lung disease cases where individuals often on hypoxic drive.

34
Q

What happens when you administer oxygen to patients with chronic lung disease?

A

Aggravates the situation

35
Q

Describe respiration during swallowing

A

Inhibited to avoid aspiration of food or fluids into the airways

36
Q

Why is swallowing followed by an expiration?

A

In order that any particles are dislodged outwards from the region of the glottis.