Infradian Rhythm

Question 1

Infradian rhythms

Answer 1

Biological rhythms which last longer than 24 hours, e.g. the Infradian rhythmsmenstrual cycle

Question 2

Menstrual Cycle

Answer 2

The menstrual cycle is a key example of an infradian rhythm, occurring less than once a day, typically every 28 days (ranges from 24–35 days).

It is governed by hormonal changes:

Oestrogen rises in the first half of the cycle, triggering the release of an egg (ovulation).

After ovulation, progesterone helps the womb lining thicken, preparing for pregnancy.

If pregnancy does not occur, hormone levels drop, the lining is shed, and menstruation begins.

The cycle begins on day one of menstruation and ends the day before the next period.

Question 3

SAD

Answer 3

seasonal affective disorder (SAD) which is said to be caused by the disruption of the sleep-wake cycle. This is as a result of changes in the daily sunlight hours because of changes in the seasons.

Question 4

A03 - Menstrual Cycle

Answer 4

-Although the menstrual cycle is said to be controlled only by internal factors (hormone levels), there has been research to show it can also be influenced by external factors.
-Stern and Mclintock found that menstrual cycles might synchronise as a result of female pheromones.

-This is because they found that when women with a history of irregular periods applied samples of pheromones from other women, 68% of women experienced changes to their own cycle - usually bringing them closer to the person who they took pheromones from.

• This shows how the menstrual cycle can be affected by numerous factors, which suggest there needs to be more research in understanding the complexity of factors affecting infradian rhythms.

Question 5

A03 - SAD

Answer 5

Additionally, research into infradian rhythms has had positive, practical applications such as the use of phototherapy as a treatment for people suffering with SAD. By using a strong light to mimic the sun rising, the melatonin levels in people with SAD are reset which relieves symptoms in up to 60% of sufferers, suggesting that there is a strong influence of external factors on this infradian rhythm. However, the therapy does not work for 40% of people which suggests that there must be other factors causing SAD in people, limiting the usefulness of phototherapy. This means that there needs to be more research and consideration of other factors that affect and impact infradian rhythms in order to find a more effective treatment.