AO1

• An infradian rhythm takes longer than

  -a day to complete
• What is an example?

  -The female menstrual cycle is an example of an infradian rhythm, as the changes in hormones that govern ovulation takes about 28 days to complete.
• during each cycle levels of

  -oestrogen cause the ovary to develop an egg and then release it (ovulation).
• After ovulation

  -progesterone helps the lining of the womb to thicken, preparing the body for pregnancy. 
• If fertilisation does not occur

  -the egg is absorbed into the body and the lining comes away and is shed (menstruation). 
• Although the menstrual cycle is an endogenous system

  -research has takenplace to suggest it can be influenced by exogenous factors, such as the cyclesof other women.
• Stern & McClintock (1998)

  -conducted a study on 29 females with a history of irregular periods. Samples of pheromones were gathered from 9 of the women, at different stages in their cycles, by placing cotton pad in their armpit.

  -Pads were worn for at least 8 hrs
• The pads were then

  -treated with alcohol and then frozen
• On day one

  -pads from the start of the menstrual cycle were rubbed on the upper lip of the 20 participants, on day two they were all given a pad from the second day of the cycle and so on. 
• They found that

  -that 68% of participants experienced changes to their cycle, which bought them closer to the cycle of the pheromone donor. Stern and McClintock demonstrated how menstrual cycles may synchronise due to the influences of female pheromones. 
• What is SAD (Seasonal affective disorder )

  -depressive disorder which follows seasonal patterns

  -It has similar symptoms to other forms of depression; persistent low mood and general lack of activity and interest in life. 
• What is SAD often described as

  -winter blues as the symptoms are triggered during the winter months when the hours of daylight decrease. 
• SAD is what type of infradian rhythm

  -circannual rhythm (as it is a yearly cycle)
• Can also be described as a circadian rhythm as it may be due to the

  -disruption of the sleep/wake cycle caused by prolonged periods of darkness during winter months. 
• What hormone is implicated in the cause of SAD

  melatonin
• During the night the pineal gland

  -secretes the hormone melatonin until there is an increase in light

  -During the winter, this process continues for longer because dawn is later.
• This has a knock on effect on

  -the production of serotonin, which is linked to the onset of depression. 
• Define an Ultradian rhythm

  -occurs more than once every 24 hours, therefore, may be several times a day.
• How many stages of the sleep cycle have been identified

  -5 that span 90 mins
• What happens during stage 1

  - brainwave patterns start to become slower and more rhythmic (theta waves)
• What happens during stage 2

  -light sleep, where a person maybe easily woken.
• What happens during stage 3 and 4

  -delta waves appear, which are slower still and have a greater amplitude. This is deep sleep, and it is difficult to wake someone up at this point.
• What is stage 5 (REM SLEEP)

  -the body is paralysed, but brain activity speeds up. It is highly correlated with the experience of dreaming.

  -REM stands for rapid eye movement and during this stage the eyes move jerkily under the eyelids.