Wakefulness and sleep
Sleep occurs in two steps. First one is Non-Rapid Eye Movement (NREM) and another is Rapid Eye Movement (REM).
NREM
This also occurs in 4 stages
- Stage 1 lasts about 7 min and can be interrupted by any small noise.
- Stage 2 lasts for 15-25 min and may interrupt by intense noise.
- Stage 3 and 4 lasts for about 25-40 min. These are deep sleep or slow wave sleep.
REM
- This become longer progressively
- Dreaming occurs in this phase
- Nervous system is activated
- Low muscle tone
Stage 0 is wakefulness stage. It is also called fully alert stage.
Mechanism of sleeping and wakefulness
- Regulated by circadian system
This regulates wakefulness .this decrease during sleeping time.
This is due to:
- Change in adrenaline concentration
- Increase in adrenaline concentration: wakeful
- Decrease in adrenaline concentration : sleep
- Change in temperature
- Increase in body temperature: wakeful
- Decrease in body temperature: sleep