ultradian infradian rhythms

Question 1

what are infradian rhythms? what are some examples?

Answer 1

Infradian rhythms last longer than 24 hours and can be weekly, monthly or annually.

Examples include:
Female menstrual cycle
Seasonal affective disorder
Hibernation (in animals)

Question 2

menstrual cycle

Answer 2

• monthly infradian rhythm - regulated by hormones
• ovulation occurs (roughly) halfway through cycle, when oestrogen levels are highest. usually lasts for 16-32 hours.

after ovulation, progesterone levels increase, ready for possible embryo implantation.

• typical menstrual cycle is approx. 28 days; however, there is considerable variation, 23 days to 36 days.

Question 3

seasonal affective disorder (SAD)

Answer 3

infradian rhythm related to the seasons (yearly cycle).

Melatonin is secreted by the pineal gland at night.
Longer nights = increased melatonin secretion
Linked to increase in depressive symptoms

Question 4

evaluating infradian rhythms

Answer 4

russell et al. (1980) found that female menstrual cycles became synchronised with other females through odour exposure. In one study, sweat samples from one group of women were rubbed onto the upper lip of another group. Despite the fact that the two groups were separate, their menstrual cycles synchronized.
suggests that the synchronization of menstrual cycles can be affected by pheromones (exogenous zeitgeber), which have an effect on people nearby rather than on the person producing them

Question 5

what are ultradian rhythms?

Answer 5

last fewer than 24 hours.
e.g Human sleep patterns
Meal patterns

Question 6

how do human sleep patterns work?

Answer 6

90 min cycles up to 5 full cycles per night
Stages 1 and 2 are ‘light sleep’ stages: brain patterns become slower (starting with alpha waves, progressing to theta waves).
Stages 3 and 4 are ‘deep sleep’ or slow wave sleep stage (associated with delta waves).
Stage 5 is REM (or dream sleep). Body is paralysed; desynchronised brain waves.

Question 7

meal patterns

Answer 7

Most humans eat three meals a day and appetite rises and falls because of food consumption.

Question 8

evaluating ultradian rhythms

Answer 8

Randy Gardener remained awake for 264 hours.
After this experience, Randy slept for just 15 hours and over several nights he recovered only 25% of his lost sleep. Interestingly, he recovered 70% of Stage 4 sleep, 50% of his REM sleep, and very little of the other stages.
Results highlight the large degree of flexibility in terms of the different stages within the sleep cycle and the variable nature of this ultradian rhythm.