Infradian and Ultradian Rhythms

Question 1

Infradian Rhythm-

Answer 1

Frequency of less than one cycle in 24 hours, such as menstruation and seasonal affective disorder

Question 2

Menstrual cycle- (infradian)

Answer 2

-governed by monthly changes in hormone levels which regulate ovulation
-cycle refers to the time between the first day of a woman’s period (uterine lining is shed) to the day before her next period
-approximately 28 days
-levels of oestrogen cause then ovary to develop an egg and release it (ovulation)

Question 3

Synchronising the menstrual cycle

Answer 3

Although the menstrual cycle is endogenous, evidence suggests that it ma y be influenced by exogenous factors such as the cycle of other women.

Question 4

McClintock (1998)

Answer 4

demonstrated how menstrual cycles may synchronise as a result of the influence of pheromones
-studied 29 women with a history of irregular periods - samples of pheromones were gathered from 9 of the women at different stages of their menstrual cycle and rubbed on the upper lip of other ppts
-68% of women experienced changed to their cycle

Question 5

Seasonal affective disorder (infradian)

Answer 5

-depressive disorder which has a season pattern of onset, described and diagnosed as a mental disorder in DSM-5
-main symptoms are persistent low mood alongside general lack of activity and interest in life
symptoms triggered during winter months when daylight hours become shorter - pineal gland secretes melatonin at night until there’s an increase in light at dawn (winter: less light = longer secretion) - has a knock on effect on production of serotonin in the brain

Question 6

Strength of infradian rhythms + RESEARCH ON MENSTRUAL CYCLE SHOWS ITS EVOLUTIONARY BASIS

Answer 6

may have been advantageous for females to menstruate together + become pregnant at the same time - would allow babies who lost their mothers to have access to breast milk + improve their chances of survival - suggests synchronisation is an adaptive strategy

Question 7

limitation of infradian rhythms- METHODOLOGY USED IN SYNCHRONISATION STUDIES

Answer 7

many factors may change a woman’s menstrual cycle (acting as confounding variables) such as stress, diet and exercise - any supposed pattern may occur by chance + may be why other studies haven’t replicated the original findings - suggest menstrual synchrony studies are flawed

Question 8

Strength of infradian rhythms + REAL WORLD APPLICATION

Answer 8

-one of the most effective treatments for SAD being light therapy - used to reset the body internal clock. Studies show this helps reduce the effects of SAD in about 80% of people (sanassi)

Question 9

Example of ultradian rhythm

Answer 9

stages of sleep -sleep pattern occurs in 90 minute periods, divided into 5 stages each characterised by a different level of brainwave activity (monitored by EEG)

Question 10

stages of sleep -

Answer 10

stage 1: light sleep (easily woken) - brain waves are high frequency + have a short amplitude, alpha waves

stage 2: alpha waves continue but have occasional random changes in pattern - sleep spindles

stage 3 + 4: deep sleep/slow wave sleep (SWS) - individual waves have lower frequency + higher amplitude (difficult to wake someone at this point)

stage 5: REM sleep - body paralysed but brain activity closely resembles the awake brain - produces theta waves + eyes occasionally move around (rapid eye movements) - dreams most often experienced but may also occur in deep sleep

Question 11

strength of ultradian rhythms + UNDERSTANDING AGE-RELATED CHANGES IN SLEEP

Answer 11

SWS reduces with age as growth hormone is produced during it (deficient in older people) - research suggests the reduces sleep may explain impairments in old age (SWS sleep can be improved using relaxation + medication) - suggests knowledge of ultradian rhythms has practical value