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Respiratory Physiology > Control of ventilation > Flashcards

Control of ventilation Flashcards

1
Q

Ventilatory control requires the stimulation of…

A

Skeletal muscles of inspiration

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2
Q

What stimulates the skeletal muscles of inspiration?

A

Phrenic nerve (to diaphrgam)

Intercostal nerves (to external intercostal muscles)

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3
Q

The neural activity of rhythmic breathing is triggered by what neurones?

A

Medullary inspiratory neurones

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4
Q

Breathing is triggered by the medullary inspiratory neurones with…

A

Voluntary override

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5
Q

Ventilatory control resides within ill-defined centres located in the…

A

Pons and medulla (respiratory centes)

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6
Q

Is ventilatory control normally conscious or subconscious?

A

Normally subconscious but can be subject to voluntary modulation

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7
Q

If the spinal cord was severed above the origin of the phrenic nerve, what would happen to breathing?

A

Breathing would cease

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8
Q

Where is the origin of the phrenic nerve?

A

C3-5

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9
Q

What are the functions of respiratory systems?

A

To set an automatic rhythm of breathing

To adjust this rhythm in response to stimuli

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10
Q

How do respiratory systems set an automatic rhythm of breathing?

A

Through co-ordinating the firing of smooth and repetitive bursts of action potentials in the dorsal respiratory group (DRG) which supply the inspiratory muscles via the phrenic and intercostal nerves

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11
Q

What modulates the rhythm of respiratory centres?

A

Emotion

Voluntary override

Mechano-sensory input from the thorax (e.g. stretch reflex)

Chemical composition of the blood (PCO2, PO2 and pH, detected by chemoreceptors)

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12
Q

The rhythm of respiratory centres is modulated by emotional input by what system?

A

The limbic system in the brain

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13
Q

Voluntary over-ride of the rhythm of respiratory centres requires input from…

A

The higher centres in the brain

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14
Q

Out of the 4 things that modulate the rhythm of respiratory centres, which is most significant?

A

The chemo-receptor input

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15
Q

What does the ventral respiratory group (VRG) of neurons supply?

A

Tongue
Pharynx
Larynx
Expiratory muscles

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16
Q

Where are central chemoreceptors located?

A

Medulla

17
Q

Central chemoreceptors detect changes in the concentration of what ions in the CSF around the brain?

A

H+ ions

18
Q

Why do the central chemoreceptors detect changes in the concentration of H+?

A

As it directly reflects the PCO2 which is the primary ventilation drive

19
Q

Where are the peripheral chemoreceptors found?

A

Carotid and aortic bodies

20
Q

What do the peripheral chemoreceptors respond to?

A

Mainly to plasma H+ conc and PO2

Less so to PCO2

21
Q

What do central chemoreceptors cause following a rise in [H+]?

A

Reflex stimulation of ventilation

22
Q

What is the term that refers to raised PCO2

A

Hypercapnea

23
Q

What effect will a decrease in arterial PCO2 have on ventilation?

A

Ventilation is reflexly inhibited therefore ventilation rate is slowed

24
Q

What do central chemoreceptors NOT respond to?

A

Direct changes in plasma H+ conc.

25
Q

What changes do peripheral chemoreceptors detect?

A

Changes in arterial PO2 and [H+]

26
Q

Peripheral chemoreceptors cause reflex stimulation of ventilation when…

A

There is a a significant fall in arterial PO2 or a rise in [H+]

27
Q

Do peripheral chemoreceptors respond to arterial PO2 or oxygen content?

A

Arterial PO2

28
Q

What usually accompanies a rise in arterial PCO2?

A

Increased H+ conc.

29
Q

Changes in plasma pH will alter ventilation through what pathways?

A

Peripheral chemoreceptor pathways

30
Q

If plasma pH falls, ventilation will be…

A

Stimulated

31
Q

What effect does alkalosis have on ventilation?

A

Inhibits it

32
Q

A large degree of voluntary control over breathing is allowed by…

A

Descending neural pathways from cerebral cortex to respiratory motor neurons

33
Q

Can we override involuntary stimuli like arterial PCO2 or H+ conc?

A

No, we can’t

34
Q

What effect does hyperventilation have on ventilation?

A

Ventilation is reflexly inhibited by an increase in arterial PO2 or a decrease in arterial PCO2

35
Q

What common drugs depress respiratory centre and can result in death following an overdose?

A

Barbiturates

Opioids

36
Q

What effect does gaseous anesthetic agents have?

A

Increase RR, but decrease Tidal Volume so decrease Alveolar Ventilation

37
Q

What effect does nitrous oxide have on peripheral chemoreceptor response to falling PaO2? Is this safe or dangerous?

A

It blunts the response

Safe in most patients, problematic in chronic lung disease cases where individual often on “hypoxic drive”

38
Q

Respiration is inhibited during swallowing to avoid what?

A

Aspiration of food or fluids into the airways

39
Q

Swallowing is followed by an expiration because?

A

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

Respiratory Physiology (13 decks)

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