rhythms that have a duration of over24 hours, and may be weekly, monthly, or even annually
ultradian rhythms
rhythms that last less than 24 hours
2 examples of infradian rhythms
the menstrual cycle
seasonal affective disorder (SAD)
what happens during the menstrual cycle
lasts around 28 days and releasesoestrogen- causes uterus lining to build up
the luteinising hormone causes egg to be released
then progesterone released to thicken womb lining
if pregnancy doesn't occur egg is absorbed and womb liningbreaks down-menstrual flow
Seasonal Affective Disorder (SAD)
a seasonal variation in mood with some people becoming severely depressed during wintermonths - melatonin is secreted from the pineal gland and has an affect on serotonin and mood
2 examples of ultradian rhythms
sleep cycle (every 90 minutes)
the basic rest activity cycle (BRAC)
5stages of sleep
first 4 stages= NREM (non-rapideyemovement)
1 and 2-> light sleep
3 and 4-> deep sleep
last stage= REM (rapideyemovement)-> when dreaming occurs. brain activityspeedsup significantly
the basic restactivity cycle
a 90-minuterhythm cycle characterised by a period of alertness followed by a spell of fatigue. this occurs every90 minutes throughout the day
evidence for the influence of exogenousfactors on our menstrualcycle: Stern and Mclintock (1998)
aimed to investigate whether women's cycles would synchronise as a result of the influence of femalepheromones
they took a group of women who had irregularperiods and gathered a sample of pheromones from 9 of the women by using cotton pads and placing under their arms for 8hours
these were then frozen and wiped under the noses of 20otherwomen
it was found that 68% of the women experienced changes to their cycles which were more in sync with their pheromone donor