10/12/25, 4:11 PM Biological rhythms: Ultradian
Biological rhythms: Ultradian
Ultradian
¬ a biological rhythm that occurs more than once in a day, taking less than 24 hours to
complete one cycle. Examples are the sleep cycle
The sleep cycle lasts for around 90 minutes, with 5 stages, each having its own
characteristics such as brain waves and physiological effects.
Types of brain waves
Brain waves are monitored using EEGs, and there are 5 types:
Alpha - wakeful rest, meaning brain is relaxed but active (Stage 1)
Beta - alert and working, involved with conscious thought (REM)
Theta - drowsy (Stage 2)
Delta - sleepy and dreaming (Stage 3 and 4)
Gamma (don't need to know this)
https://app.vaia.com/studyset/17951934/summary/71357449/edit 1/6
,10/12/25, 4:11 PM Biological rhythms: Ultradian
notice how REM and awake is
mostly the same, and stage 4 is
entirely different
https://app.vaia.com/studyset/17951934/summary/71357449/edit 2/6
,10/12/25, 4:11 PM Biological rhythms: Ultradian
Stages of sleep
Stage 1:
- Light sleep, can easily be woken up
- Physiological changes where breathing and heart rate slows down and muscles relax,
body temperature decreases
- Hypnagogia: hallucinations
- Alpha waves, relaxed but awake
Stage 2:
- Light sleep, can easily be woken up
- Drowsy state, Theta waves, with occasional bursts of activity, called sleep spindles
and K complexes
- Same physiological changes as above
Stage 3:
- Deep sleep, difficult to wake person up, they're unresponsive of external stimuli
- Delta waves
Stage 4:
- Delta waves, slow-wave sleep
- Very deep sleep
- This is when sleep walking or sleep talking often occurs
- Rhythmic breathing, limited muscle activity, body temperature at its lowest,
Stage 5:
- REM sleep, rapid-eye movement
- Brain waves speed up, Beta waves
- Difficult to wake this person up in this stage, although brain is very active as when
awake
https://app.vaia.com/studyset/17951934/summary/71357449/edit 3/6
, 10/12/25, 4:11 PM Biological rhythms: Ultradian
- Heart rate increases, breathing is rapid and shallow, and then sudden gasps
- Often dreaming occurs in this stage
So here we go from Stage 1 to 2 to 3 to 4, then backwards, 3, 2, but
not 1, instead we go into REM, and then repeat. The number of
cycles depends on how long we sleep for, but we normally are able to
go through 5 stages before we go back into Stage 1
Sleep Spindle in stage 2
K-Complexes in stage 2
evaluation:
+ Dement and Kleitman asked volunteers to participate in a lab experiment where they
had to sleep and have their sleep patterns monitored using an EEG. Dement and
Kleitman controlled the intake of caffeine and alcohol so this would not affect their sleep
patterns. The participant would be woken up at different stages in their sleep cycles and
were asked to report on their dreams, and those participants who were able to report a
dream in vivid detail were those woken up in their REM stage, which identifies an
association between REM stage and dreaming, and means possibly that dreams occur
in the REM stage.
https://app.vaia.com/studyset/17951934/summary/71357449/edit 4/6
Biological rhythms: Ultradian
Ultradian
¬ a biological rhythm that occurs more than once in a day, taking less than 24 hours to
complete one cycle. Examples are the sleep cycle
The sleep cycle lasts for around 90 minutes, with 5 stages, each having its own
characteristics such as brain waves and physiological effects.
Types of brain waves
Brain waves are monitored using EEGs, and there are 5 types:
Alpha - wakeful rest, meaning brain is relaxed but active (Stage 1)
Beta - alert and working, involved with conscious thought (REM)
Theta - drowsy (Stage 2)
Delta - sleepy and dreaming (Stage 3 and 4)
Gamma (don't need to know this)
https://app.vaia.com/studyset/17951934/summary/71357449/edit 1/6
,10/12/25, 4:11 PM Biological rhythms: Ultradian
notice how REM and awake is
mostly the same, and stage 4 is
entirely different
https://app.vaia.com/studyset/17951934/summary/71357449/edit 2/6
,10/12/25, 4:11 PM Biological rhythms: Ultradian
Stages of sleep
Stage 1:
- Light sleep, can easily be woken up
- Physiological changes where breathing and heart rate slows down and muscles relax,
body temperature decreases
- Hypnagogia: hallucinations
- Alpha waves, relaxed but awake
Stage 2:
- Light sleep, can easily be woken up
- Drowsy state, Theta waves, with occasional bursts of activity, called sleep spindles
and K complexes
- Same physiological changes as above
Stage 3:
- Deep sleep, difficult to wake person up, they're unresponsive of external stimuli
- Delta waves
Stage 4:
- Delta waves, slow-wave sleep
- Very deep sleep
- This is when sleep walking or sleep talking often occurs
- Rhythmic breathing, limited muscle activity, body temperature at its lowest,
Stage 5:
- REM sleep, rapid-eye movement
- Brain waves speed up, Beta waves
- Difficult to wake this person up in this stage, although brain is very active as when
awake
https://app.vaia.com/studyset/17951934/summary/71357449/edit 3/6
, 10/12/25, 4:11 PM Biological rhythms: Ultradian
- Heart rate increases, breathing is rapid and shallow, and then sudden gasps
- Often dreaming occurs in this stage
So here we go from Stage 1 to 2 to 3 to 4, then backwards, 3, 2, but
not 1, instead we go into REM, and then repeat. The number of
cycles depends on how long we sleep for, but we normally are able to
go through 5 stages before we go back into Stage 1
Sleep Spindle in stage 2
K-Complexes in stage 2
evaluation:
+ Dement and Kleitman asked volunteers to participate in a lab experiment where they
had to sleep and have their sleep patterns monitored using an EEG. Dement and
Kleitman controlled the intake of caffeine and alcohol so this would not affect their sleep
patterns. The participant would be woken up at different stages in their sleep cycles and
were asked to report on their dreams, and those participants who were able to report a
dream in vivid detail were those woken up in their REM stage, which identifies an
association between REM stage and dreaming, and means possibly that dreams occur
in the REM stage.
https://app.vaia.com/studyset/17951934/summary/71357449/edit 4/6
