Bio rhythms- Infradian and ultradian rhythms

Question 1

What are infradian rhythms?

Answer 1

Biological rhythms, with a frequency of less than one cycle in 24 hours
(E.g: menstruation, seasonal affective disorder)

Question 2

What are ultradian rhythms?

Answer 2

Biological rhythm with a frequency of more than once cycle in 24 hours
(E.g: sleep stages)

Question 3

What is the menstrual cycle governed by?

Answer 3

Monthly changes in hormone levels, which regulate ovulation

Question 4

What does the ‘menstrual cycle’ refer to?

Answer 4

• The time between the 1st day of the period (when the womb lining is shed) to the day before the next period
• Approx 28 days (range= 24-35)

Question 5

What is the role of oestrogen in the menstrual cycle?

Answer 5

Rising levels cause the ovary to develop an egg and release it (ovulation)

Question 6

What is the role of progesterone in the menstrual cycle?

Answer 6

Helps the womb lining to thicken, readying the womb for pregnancy

Question 7

What happens if pregnanacy does not occur (menstrual cycle)?

Answer 7

The egg is absorbed into the body, the womb lining is shed and leaves the body (menstrual flow)

Question 8

What is the menstrual cycle regulated by?

Answer 8

• Menstrual cycle= endogenous
• Influenced by exogenous factors (e.g. the cycles of other women)

Question 9

What did Stern and McClintock study?

Answer 9

• Studied 29 women with irregular periods
• Demonstrated how menstrual cycles synchronise as a result of pheromones (chemicals used to communicate)

Question 10

What was Stern and McClintock’s procedure?

Answer 10

• Collected samples of pheromones from 9 women at different stages of their menstrual cycle via cotton pads placed in the armpit
• Cotton pads worn for at least 8 hours, treated with alcohol and frozen, to be rubbed on the upper lip of other participants
• Day 1= pads applied to all 20 women
• Day 2= all given a pad from the 2nd day of their cycle, and so on..

Question 11

What did Stern and McClintock find?

Answer 11

68% of women experienced changes to their cycle, which brought them closer to the cycle of ‘odour donor’

Question 12

What is seasonal affective disorder (SAD)?

Answer 12

• A depressive disorder which has a seasonal pattern of onset
• Referred to as ‘winter blues’ (triggered during winter months when the number of daylight hours become shorter)
• Classified as a circadian rhythm, as SAD may be due to disruption to the sleep/wake cycle

Question 13

What are the main symptoms of SAD?

Answer 13

• Persistent sad mood
• Lack of activity
• Lack of interest in life

Question 14

What is the role of melatonin in SAD?

Answer 14

• Psychologists hypothesise that melatonin is implicated in SAD
• During the night, the pineal gland secretes melatonin until dawn, when there is an increase in light
• During winter, the lack of light in the mornings mean the secretion of melatonin is longer, which has an effect on serotonin production

Question 15

Strength:
I- Research has an evolutionary base

Infradian rhythms

Answer 15

D- Menstrual synchrony can be explained by natural selection. E.g: it may have been beneficial to our distant ancestors for women to menstruate together and become pregnant at the same time. In social groups, this allows babies who had lost their mothers to access breast milk, which improves survival chances
E- Suggests synchronisation is an adaptive strategy

Question 16

Limitation:
I- Methodological limitations

Infradian rhythms

Answer 16

D- Many factors affect change to the menstrual cycle, such as: stress, diet changes, exercise. These may act as confounding variables, meaning supposed patterns of synchronisation are no more than would have been expected by chance. This explains why other studies have failed to replicate findings
E- Suggests menstrual synchrony studies are flawed

Question 17

Evaluation extra:
I- Real-world application

Infradian rhythms

Answer 17

Strength: Light therapy, which stimulates strong light to reset the internal body clock, is one of the most effective SAD treatments. Sanassi- this reduces effects of SAD in 80%. High success rate and is safe with no dangerous side effects

Limitation: Light therapy can produce headaches and eye strain.Rohan et al- positive effects of light therapy wear off over time- relapse rate of 46% over successive winters vs 27% relapse in comparison group

Question 18

What research is there on the sleep cycle as an example of ultradian rhythms?

Answer 18

• Identified 5 distinct stages of sleep
• Span approx 90 minutes
• Each stage is characterised by different levels of brainwave activity, which can be monitered using EEGs

Question 19

What are the 5 distinct stages of sleep?

Answer 19

1 and 2= Light sleep, easily woken. 1- Brain waves= high frequency, short amplitude (alpha). 2- alpha waves, occassional random pattern changes- sleep spindles

3 and 4= Deep sleep/slow wave sleep (SWS). Delta waves- lower frequency, higher amplitude . Hard to wake in this stage

5- REM sleep, body is paralysed, brain activity resembles that of the awake brain. Theta waves, eyes occassionally move- rapid eye movement (REM), dreams most experienced

Question 20

Strength:
I- Improved understanding

Ultradian rhythms

Answer 20

D- Provides an understanding of age related sleep changes. Growth hormone is mostly produced during SWS and is reduced in older people. Cauter et al- resulting sleep deficit may explain issues in old age (reduced alertness). To increase SWS, relaxation and meditation are used
E- Suggests there is value in knowledge of ultradian rhythms

Question 21

Limitation:
I- Individual differences

Ultradian rhythms

Answer 21

D- There is significant variation between people. Tucker et al found large differences between participants in terms of duration of each sleep stage (especially 3 and 4). He suggests differences are biologically determined
E- Makes it difficult to describe ‘normal sleep’ meaningfully

Question 22

Evaluation extra:
I- The sleep lab

Ultradian rhythms

Answer 22

Strength: Lab studies allow control over extraneous variables. Researchers can exclude temporary variables (noise, temperature). This ensures high internal validity, allowing for causal effects to be found

Limitation: Lab studies involve being attached to complicated machinery. May be invasive, leading to disrupted sleep. Data may lack external validity