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Flashcards in Infradian Rhythms Deck (24)
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What is an infradian rhythm?

A rhythms lasting more than 24hours periodicity


What is the main infradian rhythm?

The human menstrual cycle


How long does the human menstrual cycle last?

28 days


Outline the human menstrual cycle

Hypothalamus releases GRH which stimulates the pituitary gland to produce FSH causing follicles to mature.
The maturing follicles release oestrogen which causes the lining of the uterus. When the oestrogen reaches an optimum point, LH is produced which causes the most mature follicle to burst open and release an ovum (ovulation). An ovum is carried towards the uterus where fertilisation occurs


What does Russel (1980) show?

The role of exogenous zeitgebers in infradian rhythms


What is the main endogenous pacemaker in the human menstrual cycle?



Outline Russel (1980)

There are pheromones (odourless biochemicals in the air) which is thought to be involved in the synchronisation of menstrual cycles. They collected sweat everyday from donor, mixed it with alcohol to remove bacteria and odour, and applied it under the noses of volunteers. The menstrual cycles soon became synchronised so evidence for the role of pheromones


An advantage of Russel (1980)

Supported by McClintok (1971) who synchronised menstrual cycles through pheromones


What are the consequences of the menstrual cycle?

PMS affects you a week before menstruation begins, symptoms include depression, mood swings and aggression. Dalton (1964) found PMS associated with an increase in accidents, suicides and crime


What are 2 evaluative points about the human menstrua; cycle?

1) Exogenous zeitgebers in the form of pheromones
2) Consequences of the human menstrual cycle in terms of PMS


What did Dalton (1964) show?

PMS associated with an increase in accidents, suicides and crime


Name 2 other infradian rhythms

Seasonal Affective Disorder (SAD) and hibernation


What is Seasonal Affective Disorder?

When seasonal changes affect behaviour - feel depressed in the winter and elated during the summer


What causes Seasonal Affective Disorder?

The absence of light which increases the levels of melatonin


What evidence is there for Seasonal Affective Disorder?

Depression is most likely in northern than southern countries


What has been suggested to help Seasonal Affective Disorder?

Rosenweig suggested light therapy


What evidence is there for hibernation?

Pengelley & Fisher (1959)


Outline Pengelley & Fisher (1959)

Looked at North American ground squirrels which normally hibernate in late autumn when their body temperature drops significantly and respiration slows. They were studied in the lab, and despite constant temperature and light, hibernation still occurred suggesting endogenous


Name 2 IDA points for infradian rhythms

1) Determinist
2) Real-world application


Explain why infradian rhythms can be deterministic

PMS has been used as a legal defence as Dr Dalton has argued severe PMS is similar to a mental disorder and they should not be held responsible for their actions, suggesting it is out of our control. However, evidence that we can 'will' our rhythms to change. Born (1999) told ppts to wake up earlier than usual and found higher levels of stress hormone ACTH (waking up process) than normal at designated time and thus woke up earlier


What does Born (1999) show?

That we can 'will' our rhythms to change and thus control them


Explain the real-world application of infradian rhythms

The understanding that darkness plays a key role in SAD has led to therapies like phototherapy which uses very strong lights (equivalent to daylight) to change the levels of serotonin and melatonin. It has been reported that it relieves them of their feelings but placebo effect but Eastman (1998) found placebo condition less effective, but 32% still improved with the placebo alone


Outline Eastman (1998)

Found placebo condition less effective, but 32% still improved with the placebo alone


What does Eastman (1998) show?

Placebo condition less effective and still works to a certain extent