Biological rhythms (Infradian rhythms)

Question 1

What is an example of infradian rhythms?

Answer 1

The menstrual cycle

Question 2

Describe the menstrual cycle

Answer 2

Monthly changes in hormones levels which regulate ovulation]
A typical cycle last approximately 28 days to complete
Even though the menstrual cycle is endogenous (caused internally) it can also be affected by exogenous (external factors)

Question 3

Describe research done on menstrual cycles

Answer 3

Menstrual cycles may synchronise as a result of pheromones
Study of 29 women with irregular periods
Pheromones were gathered from 9 women during their cycle
Gathered via a cotton pad placed under the armpit, treated with alcohol and then frozen
These were then rubbed on the upper lip of the other participants - cycle 1 pad given on day 1 etc
68% of women experienced changes in their cycle - closer to their “odour donour”

Question 4

Give a strength of menstrual cycles

Answer 4

Evolutionary bias - An advantage for our female ancestors to menstruate and become pregnant at the same time - offspring can be cared for together to increase survival chances
An adaptive strategy

Question 5

Give 3 limitations of menstrual cycles

Answer 5

1. Confounding variables - Stress, changes in diet and exercise can all affect menstrual cycles
   This might explain why other studies have failed to replicate the original findings - studies lack validity
2. Animal studies - Most of the research into pheromones and sexual behaviour is based on animal studies - human behaviour remains speculative and inconclusive
3. Evolution - Schank (2004) questioned the validity of the study - too many females with synchronised cycles would be competing for the highest quality males
   Because of this, surely, avoidance of synchrony would be better

Question 6

What does ‘SAD’ stand for?

Answer 6

Seasonal Affective Disorder

Question 7

What are some symptoms of SAD?

Answer 7

Persistent low mood, general lack of activity and interest in life - diagnosed as mental disorder in DSM-5 and referred to as ‘winter blues’

Question 8

SAD can be classed as what type of rhythm?

Answer 8

Type of circannual rhythm as affected by yearly cycle but can also be classed as a circadian rhythm as it can be affected by the wake/ sleep cycle and darkness during the winter

Question 9

What hormone causes SAD?

Answer 9

The hormone melatonin causes SAD

Question 10

Explain how melatonin causes SAD

Answer 10

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 that secretion goes on for longer
This then has an effect on the production of serotonin in the brain
Low serotonin = depressive symptoms

Question 11

What is a strength of SAD?

Answer 11

Practical applications - Treatment of SAD is the use of phototherapy - a lightbox that stimulates strong light in the morning and light
One study showed 30% of sufferers had relief from their symptoms
BUT the same study used a placebo “lightbox” and got results which showed a 30% relief from symptoms
This may mean that phototherapy is only effective because of expectations