Infradian and Ultradian Rhythms

Question 1

How often do infradian rhythms occur?
Give 2 examples of infradian rhythms.

Answer 1

Less than every 24 hours.
Eg: the menstrual cycle and seasonal affective disorder

Question 2

What is seasonal affective disorder (SAD)?

Answer 2

A depressive disorder with a seasonal onset. Usually occurs in winter when levels of light are low, causing low mood and a lack of energy.

Question 3

Why is SAD sometimes referred to as a circadian rhythm?

Answer 3

It can be caused by disruption to the sleep/wake cycle, attributed to long hours of darkness in the winter.

Question 4

Explain how increased melatonin production leads to a knock on effect on seratonin production.

Answer 4

At night, the pineal gland secretes melatonin until dawn when there is an increase in light. Lack of light in the morning means melatonin is released for longer, which has a knock-on effect on serotonin production.

Question 5

How long does the menstrual cycle typically last?

Answer 5

28 Days

Question 6

Explain what the first hormone in the menstrual cycle is and what it does.

Answer 6

Oestrogen.
Causes an egg in the ovary to develop and be released.

Question 7

Explain the function of progesterone.

Answer 7

Causes the womb lining to thicken in case pregnancy occurs.

Question 8

If fertilisation does not occur, what happens to the lining of the womb?

Answer 8

It is released from the body in a period.

Question 9

Give the aim of Stern and McClintock’s study.

Answer 9

To see how menstrual cycles synchronise as a result of pheromones.

Question 10

Give the procedure of Stern and McClintock’s study.

Answer 10

Samples of pheromones were gathered from 9 different women as a cotton pad was placed under their armpit. The pads were worn for 8 hours to ensure that pheromones were picked up. The pads were then treated with alcohol and frozen, to be rubbed on the upper lip of PPTs.

Question 11

In Stern and McClintock’s study, what percentage of women experienced changes to their menstrual cycle?

Answer 11

68% of women experienced changes to their menstrual cycle.

Question 12

What is an ultradian rhythm? Give an example.

Answer 12

A cycle with a frequency of more than once in 24 hours.

Question 13

How long does a typical sleep cycle last?

Answer 13

90 minutes.

Question 14

What scanning technique is used to monitor brain activity during sleep?

Answer 14

EEG.

Question 15

Describe stage 1 and 2 of the sleep cycle.
Describe how the brainwaves on an EEG at this stage may look.
What happens in stage 2 of sleep that is slightly different to stage 1?

Answer 15

Light sleep, where a person can easily be woken.
Brainwaves have a high frequency and low amplitude, making them alpha waves.
In stage 2, sleep spindles occur which are random changes in brain activity.

Question 16

Describe stage 3 and 4 of the sleep cycle.
Describe the brainwaves that may be seen on an EEG.

Answer 16

Deep sleep/slow wave sleep. The person is harder to wake up.
Delta brainwaves occur with a low frequency and high amplitude.

Question 17

Describe stage 5 of sleep.
Describe the waves that would be seen on an EEG at this stage.

Answer 17

REM sleep, where dreams are most likely to happen. The body is paralysed but brain activity resembles that of an awake person. Eyes move around rapidly.
The brain produces theta waves.

Question 18

Explain the strength of menstrual synchrony and how it can be explained by natural selection.

Answer 18

Synchronisation of the menstrual cycle is thought to have some evolutionary value. For our distant ancestors, it may have been advantageous for women to menstruate together and become pregnant at the same time. In a social group, this would allow babies who had lost their mothers during/after childbirth to have access to milk and care, improving their chances of survival. This suggests that synchronisation is an adaptive strategy.

Question 19

Explain the strength of sleep studies being highly scientific and being conducted in labs.
What extraneous variables are able to be removed by using scientific experiments?

Answer 19

Sleep studies use highly precise, unbiased equipment in the lab, meaning there is a high degree of control over extraneous variables. This means that the researcher can exclude temporary variables such as noise or temperature that could affect sleep. However, lab studies involve PPTs to be attached to complex machinery, leading to PPTs to sleep in a way that does not represent their ordinary sleep pattern. This means that any findings may not be fully reflective of how we usually sleep.

Question 20

Explain the strength of infradian rhythm research leading to the development of successful treatments.
Use the example of phototherapy treatments used for SAD. Compare this to the effectiveness of CBT therapy

Answer 20

One of the most effective treatments for SAD is light therapy, a box which simulates very string light to reset the bodys internal clock. Studies show this helps to reduce the effects of SAD in about 80% of people. It is also preferred over antidepressants as there are no unpleasant side effects. On the other hand, there is risk of eye strain and headaches. Additionally, there is also risk of relapse, as research has found a relapse rate of 46% over successive winters, compared to 27% in a comparison group using CBT. This means that the pros and cons of treatment should be weighed up before choosing one.

Question 21

Explain the limitation of individual differences affecting ultradian rhythms.
Use the example from Tucker who found large differences between PPTs duration of each sleep stage.

Answer 21

Tucker found large differences between PPTs in terms of the duration of each sleep stage, particularly stage 3 and 4. She suggested that these differences are likely to be biologically determined. This makes it difficult to describe normal sleep in any meaningful way.