biopsychology: biological rhythms

Question 1

What is an infradian rhythm?

Answer 1

A type of biological rhythm with a frequency of less than one cycle in 24 hours
for example:
* menstruation
* seasonal affective disorder.

Question 2

What is an ultradian rhythm?

Answer 2

A type of biological rhythm with a frequency of more than one cycle in 24 hours > An example is the stages of sleep

Question 3

What is the typical duration of the menstrual cycle?

Answer 3

Approximately 28 days

The cycle starts from the first day of menstruation to the day before the next period.

Question 4

outline the menstrual cycle

Answer 4

It is governed by monthly changes in hormone levels which regulate ovulation.
* During each cycle, rising levels of the hormone oestrogen cause the ovary to develop an egg and release it (ovulation).
* After ovulation the hormone progesterone helps the womb lining to grow thicker, readying the body for pregnancy. If pregnancy does not occur the egg is absorbed into the body, the womb lining comes away and leaves the body (the menstrual flow)

Question 5

What hormone is responsible for ovulation in the menstrual cycle?

Answer 5

Oestrogen

Question 6

What role does progesterone play in the menstrual cycle?

Answer 6

Helps the womb lining to grow thicker in preparation for pregnancy > If pregnancy does not occur, the egg is absorbed and the womb lining is shed.

Question 7

Is the menstrual cycle an endogenous or exogenous system?

Answer 7

Endogenous system > It is mainly governed by internal biological processes.

Question 8

What are some exogenous factors that influence the menstrual cycle?

Answer 8

Diet, Stress

these external factors can affect hormone levels and cycle regularity

Question 9

What was the focus of the study by Kathleen Stern and Martha McClintock?

Answer 9

The influence of pheromones on menstrual cycles

Question 10

outline Stern and Mclintock’s study

Answer 10

they studied 29 women with irregular periods
Samples of pheromones were gathered from nine of the women at different stages of their menstrual cycle via a cotton pad placed in their armpit. The pads were worn for at least 8 hours to ensure the pheromones were picked up. The pads were treated with alcohol and frozen, to be rubbed on the upper lip of the other participants. On day one, pads from the start of the menstrual cycle were applied to all 20 women, on day two they were all given a pad from the second day of the cycle and so on.

Question 11

What percentage of women in the study experienced changes to their cycle due to pheromones?

Answer 11

68%

This percentage reflects those who aligned their cycles closer to that of their ‘odour donor’.

Question 12

What is seasonal affective disorder (SAD)?

Answer 12

A depressive disorder with a seasonal pattern of onset

Symptoms include persistent low mood and lack of interest in life.

Question 13

How can SAD be classified as a circadian rhythm?

Answer 13

It may be due to the disruption of the sleep-wake cycle

SAD is often triggered by shorter daylight hours in winter.

Question 14

What effect does the lack of morning light have on melatonin secretion during winter?

Answer 14

It prolongs the secretion of melatonin

This affects serotonin production in the brain.

Question 15

List some symptoms of seasonal affective disorder (SAD).

Answer 15

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

These symptoms are indicative of the disorder’s impact.

Question 16

outline Stern and McClintock’s study

Answer 16

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 via a cotton pad placed in their armpit. The pads were worn for at least 8 hours to ensure the pheromones were picked up. The pads were treated with alcohol and frozen, to be rubbed on the upper lip of the other participants. On day one, pads from the start of the menstrual cycle were applied to all 20 women, on day two they were all given a pad from the second day of the cycle and so on

Question 17

results of Stern and McClintock’s study

Answer 17

68% of women experienced changes to their cycle which brought them closer to the cycle of their ‘odour donor’ > shows the cycles of other women act as an exogenous zeitgeber

Question 18

outline seasonal affective disorder (SAD)

Answer 18

It is a depressive disorder which has a seasonal pattern of onset
symptoms include:
* Persistent low mood,
* lack of activity and interest in life

SAD can also be classed as a circadian rhythm as the experience of SAD may be due to the disruption of the sleep-wake cycle, SAD is triggered during the winter, when the number of daylight hours become shorter. 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 morning means this secretion process continues for longer. This has a knock on effect on the production of serotonin in the brain

Question 19

AO3: practical application

Answer 19

research on SAD has led to real world application
To treat SAD light therapy was created. This is a lightbox that stimulates very strong light in the morning and evening. It is thought to reset the melatonin levels in people with SAD. This has been found to relieve the symptoms in up to 60% of sufferers (Eastman et al).

STRENGTH because it shows how external cues such as light can affect the secretion of melatonin which affects your sleepwake cycle and mental state.

HOWEVER, Rohan recorded a relapse rate of 46% over successive winters, compared to 27% in a comparison group receiving CBT.
This suggests that the light therapy may not be effective as a long term solution for SAD. So perhaps there are other factors more influential in the onset of SAD.

Question 20

AO3: methodological issues

Answer 20

There are methodological issues with studies which support the idea that the menstrual cycle is influenced by exogenous factors such as synchronisation. It has been suggested there are many factors that effect change in a women’s menstrual cycle. There may be confounding variables such as:stress, changes in diet etc.

WEAKNESS because any synchronisation in menstrual cycle may have been due to chance. So we cannot establish a cause and effect relationship.This suggests that menstrual synchrony studies are flawed. Despite the lack of cause and effect relationship, we can still conclude exogenous zeitgebers affect our menstrual cycle

Question 21

AO3: evolutionary explanation

Answer 21

One strength of menstrual cycle research is that it may be explained by natural selection
Synchronisation of the menstrural cycle is thought to have 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 lost their mothers during or after childbirth to have access to breast milk, thereby improving their chances of survival.

STRENGTH as this suggests that synchronisation is an adaptive strategy.

Question 22

outline the sleep cycle

Answer 22

• an ultradian rhythm
• has 5 distinct stages
• the cycle lasts 90 minutes
• can be mointored by EEGs

Question 23

state the 5 stages of the sleep cycle

Answer 23

• stage 1
• stage 2
• stage 3
• stage 4
• stage 5/REM sleep

Question 24

what does REM stand for

Answer 24

rapid eye movement

Question 25

outline stage 1 and 2

Answer 25

. **Light sleep, where the person may be easily woken.** At the beginning of sleep, **brain wave patterns become slower** and more rhythmic **(alpha waves)** becoming **even slower as sleep becomes deeper (theta waves)**

Question 26

outline stage 3 and 4

Answer 26

Involves **delta waves** which are **slower still and have a greater amplitude than earlier wave patterns**. This is deep sleep or slow wave sleep and it is **difficult to rouse someone at this point**

Question 27

outline stage 5: REM sleep

Answer 27

The **body is paralysed** but the **brain activity speeds up**. **Eyes undergo rapid eye moment, which is fast, jerky activity** of the eyes under the eyelids. This is **associated with dreaming **

Question 28

AO3: ultradian rhythms > individual differences

Answer 28

One limitation of ultradian rhythms research is that there is **significant variations between people** **Tucker** found **large differences between participants in terms of the duration of each sleep stage**, particularly stage 3 and stage 4. He suggests that these differences are likely to be biologically determined. WEAKNESS as this suggests that it is **difficult to describe ‘normal sleep’ in any meaningful way**. So the **research cannot be generalised to explain the sleep cycle in everyone**

Question 29

AO3: improved understanding of sleep

Answer 29

research into ultradian rhythms has **improved understanding of age-related changes in sleep** Sleep scientists have observed that **slow wave sleep reduces with age**. Growth hormone is mostly produced during slow wave sleep and therefore is reduced with older people. According to **Cauter**, the **resulting sleep deficit may explain various issues with old age such as reduced alertness**. In order increase slow wave sleep, relaxation and medication may be used STRENGTH as it shows how **knowledge of ultradian rhythms has practical value** and can be used to improve peoples sleep and therefore health