Ultradian rhythms - AO1

• Ultradian rhythms are ones that take less than 24 hours and occur more than once a day, for example the sleep cycle.
• There are 5 stages of sleep which can be identified using an EEG, showing the electrical activity of the brain.
• Stages 1 and 2 involve light sleep where you can be easily woken. In stage 1 alpha waves are produced and in stage 2 alpha waves continue but with sleep spindles (occasional random changes).
• . Stages 3 and 4 involve deep sleep or slow wave sleep. The brain produces slower delta waves which have a lower frequency and higher amplitude. It is more difficult to wake someone up in these stages.
• Lastly, stage 5 is when we experience rapid eye movement (REM) sleep. The body is paralysed and the activity of the brain resembles someone who is awake. It produces theta waves and the eyes sometimes move around. This is when dreams are most likely to occur