Neurophysiology — Sleep Respiration

Current · V5 (2025) → H2.vi Historical · V4 (2023) → K1.vi 1 exam appearance

2015B Q18

Exam question

Describe the stages of sleep (50%) Describe the respiratory physiological changes that occur in sleep (50%)

CICMWrecks answer

Master answer

Slow-wave
- Deep, restful sleep occuring during first hour
- Stage I
  - As person drifts to sleep
  - α waves replaced by theta waves of low frequency (4~8Hz)
- Stage II
  - Occasional bursts of high frequency waves (sleep spindles)
- Stage III
  - High voltage, low frequency (1~2Hz) δwaves with bursts of high frequency K complexes
- Stage IV
  - Deepest sleep
  - High voltage δ waves
REM
- Rapid Eye Movements
  - Occurs every 90 minutes and lasts 30 minutes
  - β brain waves resembling alert wakefulness

Tidal volume
- Declines progressively as slow wave sleep progresses → minimal in REM sleep
- V_t 25% of awake volume during REM sleep
Respiratory Rate
- Remains relatively unchanged
- Irregular pattern during REM sleep
Response to pO₂ and pCO₂ dampened
- PaCO₂ increases 3mmHg
- PaO₂ decreases 3mmHg
Upper airway resistance
- Increased
  - Especially in REM sleep
  - At hypopharynx and soft palate
- Loss of tonic activity of tensor palati

Sakurai 2016

Answer by Sakurai

Past papers

1 appearance

Exam	Exact exam wording	Candidate success
2015B Q18	Describe the stages of sleep (50%) Describe the respiratory physiological changes that occur in sleep (50%)	29%