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INFRADIAN RHYTHMS - MENSTRUAL CYCLE - Coggle Diagram
INFRADIAN RHYTHMS - MENSTRUAL CYCLE
menstrual cycle is a monthly infradian rhythm
regulated by hormones that either promote ovulation or stimulate uterus for fertilisation
ovulation occurs halfway through cycle when oestrogen levels are at their highest, lasts 16-32 hours
progesterone levels increase after ovulation to prepare for implantation of embryo into uterus
women have considerable differences in cycle length ranging from 21-40 days
McCLINTOK
believes menstrual cycle is controlled by pheromones
sample contained 29 women with irregular periods, collected pheromones from 9 women in different stages of their cycle, pad wiped on womens lips
days 1 pad given on day 1, on day 2 different pad and so on
found 68% of women found changes in their cycle which brought them closer to the cycle of the 'odour donor'
thought this type of synchrony was an evolutionary response as it would be advantageous for women to be pregnant at the same time
controversial as menstural cycle related to changes in mood
4-5 days before bleeding (premenstrual) 60% of women experience changes (mild irritation, depression or headaches)
DALTON
summarised studies of behaviour change attributed to menstrual cycle: 63 - 84% of crimes committed by women are in premenstrual stage, accident and suicide rates increase, decline in school work
not all evidence indicates changes are due to menstrual cycle
most researchers maintain most women have little relationship between cycle and mood
mood changes of cyclical nature not confined to only women, evidence suggests that a monthly cycle also affects men - at least one study shows monthly hormonal rhythm and mood cycle in boys and men
HERSEY
believes everyone experiences cyclical mood changes, but may be unaware of them
studied 25 industrial workers for a year taking physiological and psychological observations -> found they showed emotional variation on a daily basis and also on a much longer rhythmic cycle
one 60 year old showed a 9-week cycle so gradual he believed himself to be constant in his moods