Control of Breathing (asleep)

Question 1

The body becomes functionally paralysed during REM sleep. What two muscles are spared? What implications does this have for breathing?

Answer 1

Eye muscles
Diaphragm
The accessory muscles (e.g. intercostals) are no longer active so it becomes more difficult to breathe

Question 2

What centre controls breathing and where is it located?

Answer 2

Respiratory Centre - medulla

Question 3

How does the control of breathing change when asleep compared to when awake?

Answer 3

When asleep, cortical and emotional control of breathing is inactive. It is solely regulated by the respiratory centre.

Question 4

Name a complex in the medulla that is involved in regulating the respiratory rhythm.

Answer 4

Pre-Botzinger Complex

Question 5

What models are used to determine certain neuronal control pathways?

Answer 5

Lesion Deficit Models

Question 6

How do minute ventilation and tidal volume change when asleep?

Answer 6

Minute Ventilation = DECREASES (10% reduction in minute ventilation)
Tidal Volume = DECREASES
NOTE: frequency remains roughly the same

Question 7

What plays the biggest role in the control of breathing when awake?

Answer 7

PCO2 levels

Question 8

How does oxygen saturation change when asleep? Explain your answer.

Answer 8

Oxygen saturation remains the same - because you are at the flat part of the oxygen dissociation curve meaning that despite a decrease in PO2, oxygen saturation stays the same.
NOTE: During REM sleep, you PO2 and SO2 drop slightly

Question 9

Why might this be different for someone with lung disease?

Answer 9

People with lung disease live on the steeper part of the ODC so a reduction in PO2 during sleep can cause a marked reduction in oxygen saturation.

Question 10

How do carbon dioxide levels change when you go to sleep?

Answer 10

Carbon dioxide levels rise when you go to sleep.

Question 11

How does the level of carbon dioxide required to trigger breathing change when you go to sleep?

Answer 11

INCREASES - a higher PCO2 is required to trigger breathing

Question 12

How does sensitivity to carbon dioxide change when you go to sleep?

Answer 12

Sensitivity to carbon dioxide decreases when you go to sleep - there is a smaller change in minute ventilation per 1 kPa rise in PCO2

Question 13

What is the apnoeic threshold?

Answer 13

The minimum PCO2 required to trigger breathing

Question 14

What happens if you prevent the carbon dioxide levels from exceeding the apnoeic threshold?

Answer 14

You stop breathing

Question 15

Describe the structure of the upper airways (pharynx).

Answer 15

It is a muscular collapsible tube with no cartilage rings holding it open.

Question 16

Describe what causes obstructive sleep apnoea.

Answer 16

Relaxation of the muscular parts of the upper airways, negative intraluminal pressure and positive extraluminal pressure can lead to collapse of the airways.
Muscles involved: epiglottis, tongue, pharyngeal muscles (not totally sure about this - just some suggestions)

Question 17

Describe the cycle that takes place in someone suffering from obstructive sleep apnoea.

Answer 17

Sleep –> decrease in upper airway muscle function –> apnoea –> arousal –> patent airway –> ventilation
All starts again

Question 18

How does central sleep apnoea differ from obstructive sleep apnoea?

Answer 18

This is a chemosensitivity issue rather than a mechanical obstruction

Question 19

What are the implications of sleep apnoea on heart disease?

Answer 19

Patients with sleep apnoea have to generate massive pressures in their chest to allow them to breathe and this can exacerbate heart conditions.