Ultradian And Infradian Rhythms

Question 1

What is an ultradian rhythm?

Answer 1

Rhythms which are less than 24 hours and occur more than once in 24 hours

Question 2

What are some examples of ultradian rhythms?

Answer 2

Sleep cycles
Blood circulation

Question 3

What are infradian rhythms?

Answer 3

Rhythms which last longer than 24 hours and occur less than once within 24 hours

Question 4

What are some examples of infradian rhythms?

Answer 4

The menstrual cycle
Pregnancy
Seasonal Affective Disorder

Question 5

What is an example of research into ultradian rhythms?

Answer 5

The sleep cycle

Question 6

Process of sleep cycle research + findings

Answer 6

EEG brain scans where used to monitor brain wave activity, psychologists found that there were 5 distinct stages of sleep, which all together lasted for around 90 minute cycles - this cycle then continues throughout the night

Question 7

What were the 5 stages researchers found in the sleep cycle?

Answer 7

Stage 1 - light sleep and person may be easily woken, high frequency and short amplitude alpha waves

Stage 2 - alpha waves continue, but may be occasional changes in brain waves called ‘brain spindles’

Stage 3 and 4 - known as deep sleep or slow wave sleep, delta waves high low frequency and high amplitude - hard to wake someone up

Stage 5 - body has limited muscle movement/parslysed, rapid eye movement occurs at this stage, brain is producing theta waves + closely resembles that of an awake brain

Question 8

Evaluations of ultradian rhythms:

Answer 8

• Tucker et al suggested there was a large amount of individual differences, e.g in a study carried out over 11 days they found inconsistency with sleep duration, time to fall asleep and the amount of time in each stage, meaning that sleep cycles could be biologically determined and that research may lack population validity

+ Understanding with age, slow wave sleep decreases, meaning we can use this knowledge to provide medication and treatments that can help to induce more slow wave sleep within older individuals - may be used to explain impairments, such as reduced alertness

Question 9

Menstrual cycle - infradian rhythm

Answer 9

Mensutrual cycles on average last about 28 days, halfway through the cycle ovulation occurs when oestrogen levels are high and then after ovulation, progesterone levels increase to prepare the uterus for fertilisation

Hormones such as progesterone and oestrogen help to regulate the menstrual cycle

Question 10

SAD - infradian rhythm

Answer 10

Seasonal affective disorder usually occurs around winter, when the amount of light is low
This can cause for there to be more secretion of melatonin, which in turn cause low mood and depressive behaviour

This can be treated through phototherapy by increasing the amount of light the body receives, therefore lowering the production of melatonin

Question 11

Evaluation of infradian rhythms

Answer 11

+ treatments - phototherapy for SAD, said to have reduced effects by 80%

+ may be an evolutionary basis, e.g when women lived together and did not take oral contraception it had been found that their menstrual cycles would often link up, meaning this could have an evolutionary basis, as in cases where a mother dies - the other mothers are capable of caring for that child by providing breast milk

• Methodological issues, research failed to take into consideration confounding variables, e.g stress and diet which can impact infradian rhythms - not only biologically determined