Discuss research into ultradian rhythms. (16 marks)
Ultradian rhythms are biological rhythms that last fewer than 24 hours, and they are cycles
that occur more than once every 24 hours. This differs from circadian rhythms, which
include the sleep-wake cycle, and is the 24-hour biological rhythm that is reset by levels of
light.
An example of ultradian rhythms is appetite or meal patterns in humans. Most humans eat
three meals a day and appetite rise and falls because of food consumption.
Another ultradian rhythm would be the human sleep cycle. This cycle alternated between
REM (rapid eye movement) and NREM (non-rapid movement) sleep and consists of five
stages. The cycle starts at light sleep, progressing to deep sleep, and then REM sleep, where
brain waves speed up and dreaming occurs. This cycle repeats itself about every 90 minutes
throughout the night. An average person can experience up to five full cycles in a night.
A complete sleep cycle goes through 4 stages of NREM sleep before entering REM (stage 5)
and then repeats itself. Research using EEG has highlighted distinct brain wave patterns
during the different stages of sleep. Stage 1 and 2 are ‘light sleep’ stages, during which
brainwave patterns become slower and more rhythmic, starting with alpha waves progress
to theta waves. Stage 3 and 4 are ‘deep sleep’ or slow wave sleep stages, where it is difficult
to wake someone up. This stage is associated with slower delta waves. Finally, Stage 5 is
REM (or dream) sleep. The body is paralyzed (to stop the person acting out their dream) and
brain activity resembles that of an awake person.
There are individual differences in ultradian rhythms amongst different people. In Tucker et
al. (2007), he conducted research on sleep cycles of healthy 22-40 year old people. He found
significant differences in results between different participants in terms of the duration of
each stage, particularly stages 3 and 4 (just before REM sleep). This demonstrates that there
may be innate individual differences in ultradian rhythms, which means that it is worth
focusing on these differences during investigations into sleep cycles. This also means that
Ultradian rhythms are biological rhythms that last fewer than 24 hours, and they are cycles
that occur more than once every 24 hours. This differs from circadian rhythms, which
include the sleep-wake cycle, and is the 24-hour biological rhythm that is reset by levels of
light.
An example of ultradian rhythms is appetite or meal patterns in humans. Most humans eat
three meals a day and appetite rise and falls because of food consumption.
Another ultradian rhythm would be the human sleep cycle. This cycle alternated between
REM (rapid eye movement) and NREM (non-rapid movement) sleep and consists of five
stages. The cycle starts at light sleep, progressing to deep sleep, and then REM sleep, where
brain waves speed up and dreaming occurs. This cycle repeats itself about every 90 minutes
throughout the night. An average person can experience up to five full cycles in a night.
A complete sleep cycle goes through 4 stages of NREM sleep before entering REM (stage 5)
and then repeats itself. Research using EEG has highlighted distinct brain wave patterns
during the different stages of sleep. Stage 1 and 2 are ‘light sleep’ stages, during which
brainwave patterns become slower and more rhythmic, starting with alpha waves progress
to theta waves. Stage 3 and 4 are ‘deep sleep’ or slow wave sleep stages, where it is difficult
to wake someone up. This stage is associated with slower delta waves. Finally, Stage 5 is
REM (or dream) sleep. The body is paralyzed (to stop the person acting out their dream) and
brain activity resembles that of an awake person.
There are individual differences in ultradian rhythms amongst different people. In Tucker et
al. (2007), he conducted research on sleep cycles of healthy 22-40 year old people. He found
significant differences in results between different participants in terms of the duration of
each stage, particularly stages 3 and 4 (just before REM sleep). This demonstrates that there
may be innate individual differences in ultradian rhythms, which means that it is worth
focusing on these differences during investigations into sleep cycles. This also means that
