Biological rhythms: Infradian & Ultradian rhythms

Question 1

What is an infradian rhythm?

Answer 1

A type of biological rhythm with a frequency of less than 1 cycle every 24 hours

Question 2

What is an example of an infradian rhythm?

Answer 2

The menstrual cycle which is governed by monthly changes in hormone levels which regulate ovulation

Question 3

What has research shown about the menstrual cycle?

Answer 3

Although it is an endogenous system it may be influenced by exogenous factors like the cycles of other women

Question 4

What was Stern & McClintock’s (1998) study?

Answer 4

• involved 29 women with irregular periods
• samples of pheromones taken from 9 at different stages of their cycle by a cotton pad placed in their armpit
• the pads were worn for at least 8 hours to ensure pheromones were picked up
• pads were then treated with alcohol & froze to be rubbed on the upper lip of other pps
• on day 1 pads from start of menstrual cycle given to all women then so on
• McClintock found that 68% women experienced changes to their cycle which brought them closer to the cycle of their ‘odour donor’

Question 5

What is seasonal affective disorder (SAD)?

Answer 5

• a depressive disorder which has a seasonal pattern and is described & diagnosed as a mental disorder
• main symptoms are persistent low mood & general lack in activity or interest in life
  symptoms are triggered during winter months when when no. of daylight hours are shorter
• SAD is a circannual rhythm as it it subject to a yearly cycle but also classed as a circadian rhythm since it may be due to disruption of sleep/wake cycle

Question 6

What have psychologists hypothesised about SAD?

Answer 6

Melatonin could be the cause of it since during the winter the lack of light leads to the secretion of melatonin continuing longer which could also have an effect on the production of serotonin (has been linked to onset of depressive symptoms)

Question 7

What is an ultradian rhythm?

Answer 7

A type of biological rhythm with a frequency of more than 1 cycle every 24 hours

Question 8

What is an example of an ultradian rhythm?

Answer 8

The stages of sleep

Question 9

How many distinct stages of sleep are there?

Answer 9

• psychologists have identified 5 stages that span approx. 90 minutes altogether
• each stage is characterised by a different level of brainwave activity monitored using an EEG

Question 10

What happens in Stages 1 and 2 of the sleep cycle?

Answer 10

• light sleep where person may be easily woken
• at the beginning of sleep brainwave patterns start becoming more slower & rhythmic (alpha waves)
• waves become even slower and sleep deepens (theta waves)

Question 11

What happens in Stages 3 and 4 of the sleep cycle?

Answer 11

• involved delta waves which are slower & have greater amplitude than previous wave patterns
• this is deep sleep and is difficult to wake someone up at this point

Question 12

What happens in Stage 5 (REM sleep) of the sleep cycle?

Answer 12

• body is paralysed yet brain activity speeds up in a way that resembles the awake brain
• REM means rapid eye movement as the activity of the eyes is very fast at this point
• research has correlated that REM activity during sleep is related to dreaming

Question 13

Evaluation: Methodological limitations in synchronisation studies

Answer 13

• commentators argue that there are many factors that effect the menstrual cycle like stress & changes in diet which may ac as confounding variables
• this means any supposed synchronisation patterns could have occurred by chance
• research involves a small sample of women & replies on pps self-reporting the start of their cycle

Question 14

Evaluation: Evidence supports the idea of distinct stages in sleep

Answer 14

• study by Dement & Kleitman (1957) monitored sleep patterns of 9 adults in a sleep lab
• brainwave activity recorded using EEG and researchers controlled effect of caffeine & alcohol
• REM activity highly correlated to dreaming
• brain activity varied according to how vivid dreams were & pps woken during dreaming reported accurate recollections of their dreams
• replications of study noted similar findings therefore study suggests that REM sleep is an important component of the ultradian sleep cycle

Question 15

Evaluation: Animal studies

Answer 15

• most of the knowledge of pheromones on behaviour comes from animal studies
• role of pheromones in animal sexual selection is well documented - sea urchins release pheromones into surrounding water so other urchins in the colony eject their sex cells simultaneously

Question 16

Evaluation: Practical application to SAD

Answer 16

• one of the most effective treatments of SAD is phototherapy
• this is a lightbox which stimulates strong light in the morning & evening
• is thought to reset melatonin levels in people with SAD, relieving symptoms in up to 60% of individuals