Infradian and Ultradian Rhythms

Question 1

What is an infradian rhythm?

Answer 1

A biological rhythm that takes less than a day.

Question 2

Give an example of an infradian rhythm.

Answer 2

Menstrual cycle and SAD.

Question 3

Why is the menstrual cycle an infradian rhythm?

Answer 3

Because it’s 28 days (longer than 24 hours).

Question 4

Outline the infradian rhythm: menstrual cycle.

Answer 4

1. Rising levels of oestrogen cause ovulation (the ovary to develop and release an egg.
2. Then progesterone helps the womb lining to thicken, readying the body for pregnancy.
3. If pregnancy doesn’t occur, the egg is absorbed into the body and the womb lining comes away and leaves the body as menstrual flow.

Question 5

How can exogenous zeitgebers affect the infradian rhythm: the menstrual cycle?

Answer 5

Stern and McClintock studied 29 women with irregular periods. Pheromones were rakes from some at different stages of their cycles.
These pads were cleaned with alcohol and later rubbed on the upper lips of other pps.
68% of women experienced changes to their cycle which brought them closer to the cycle of their odour donor.

Question 6

What is an ultradian rhythm?

Answer 6

A biological rhythm that takes less than a day.

Question 7

Give an example of ultradian rhythms.

Answer 7

Stages of sleep.

Question 8

The stages of sleep are an ultradian rhythm. Outline the different stages.

Answer 8

1 & 2 - light sleep. Brainwaves become slower and more rhythmic (alpha waves), slowing down further as sleep scones deeper (beta waves).
3 & 4 - difficult to rouse someone. Deep sleep characterised by delta waves which are slower and have greater amplitude.
5 - REM. Body paralysed yet brain activity speeds up. Fast jerky activity of eyes.