Biopsychology - 9) Biological Rhythms: Infradian and Ultradian Rhythms Flashcards
Infradian rhythm
Biological rhythm that takes longer than 24 hours (can be weekly, monthly, annually etc)
Example of an infradian rhythm
Female menstrual cycle
Menstrual cycle
Time between the first day of a women’s period and the day before her next period
Duration of menstrual cycle
Anywhere between 24 and 35 days (generally 28 days)
Hormones involved in the menstrual cycle
Oestrogen levels rise causing egg to be released and for ovulation to occur
Progesterone helps womb lining grow thicker, readying body for pregnancy
Menstrual flow
If pregnancy doesn’t occur, the egg is absorbed in the body and the womb lining comes away to leave the body
Who carried out research into the menstrual cycle?
McClintock and Stern
Aim of McClintock and Stern’s research into the menstrual cycle
To investigate whether or not the menstrual cycle can be influenced by exogenous zeitgebers
Sample of McClintock and Stern’s research into the menstrual cycle
29 women with history of irregular periods
Process of McClintock and Stern’s research into the menstrual cycle
Samples of pheromones (chemicals) gathered from 9 of the women at different stages of menstrual cycle
Day 1 - pads from start of menstrual cycle applied to all 20 women
Day 2 - pads from day 2 applied on all 20 women and so on
Findings of McClintock and Stern’s research into the menstrual cycle
68% of the 20 women experienced changes to their cycle as a result of the pheromones
Conclusion of McClintock and Stern’s research into the menstrual cycle
Exogenous zeitgebers can impact the female menstrual cycle
Examples of an infradian rhythm other than the menstrual cycle
Seasonal Affective Disorder (SAD)
What is SAD?
Infradian rhythm related to the seasons
People feel depressive symptoms during winter months
What neurotransmitter is involved in SAD?
Melatonin
Melatonin’s involvement in SAD
Melatonin is secreted by pineal gland
Longer nights in winter increases this secretion
More melatonin linked to increase in depressive symptoms
The role of exogenous zeitgebers in SAD
Patients of SAD waking up to an artificial bright light reported an improvement in their depression symptoms
Ultradian rhythm
Biological rhythm that takes less than 24 hours
Examples of ultradian rhythm
Stages of sleep
How many stages of sleep are there and what are they?
5 stages:
- stages 1 and 2 are non-REM
- stages 3 and 4 are non-REM
- stage 5 is REM
How long does each stage of sleep last?
Approximately 90 minutes
What is each stage of sleep characterised by?
A different level of brainwave activity which can be monitored using an EEG
Stages 1 and 2 of the stages of sleep
Light sleep
Individual woken easily
Brainwave patterns become slower and more rhythmic (alpha waves)
Patterns become even slower as sleep becomes deeper (theta waves)
Stages 3 and 4 of the stages of sleep
Deep sleep / slow wave sleep (delta waves)
Difficult to wake someone up during these stages
Stage 5 of the stages of sleep
REM sleep
Body is paralysed
Brain activity speeds up significantly to resemble that of awake brain
REM activity during sleep highly correlated with dreaming
Who conducted research into the stages of sleep?
Dement and Kleitman
Process and Dement and Kleitman’s research into the stages of sleep
Brain activity of 0 participants measured using EEG
Participants weren’t influenced by alcohol or caffeine
Results of Dement and Kleitman’s research into the stages of sleep
REM sleep highly correlated to dreaming
When he woke up people during REM stage, they could recall very clearly what they dreamed
Non-sleep research into ultradian rhythms
During the day we move from states of alternates into states of fatigue every 90 minutes
The human mind can concentrate for 90 minutes but after this the body runs out of resources
