Ultradian rhythm: a type of biological rhythm with a frequency of more than one cycle every 24 hours, for example, the stages of sleep and the cycle of hunger
It takes approximately 90 minutes to run through one sleep cycle
Stages 1 and 2
- The 'sleep escalator'
- The person may be easily woken
- An EEG would show brain wave patterns becoming slower and more rhythmic (alpha waves), and as sleep becomes deeper, theta waves are recorded