Biological rhythms - Infradian and ultradian

infradian rhythms

a type of biological rhythm w a frequency of less than one cycle in 24 hrs such as menstruation

menstrual cycle

governed by monthly changes in hormone levels which regulate ovulation during each cycle-rising levels of the hormone oestrogen cause the ovary to develop an egg and release it then progesterone helps the womb lining to grow thicker

research into infradian rhythms

evidence suggests the menstrual cycle may be influenced by exogenous factors-such as cycles of other women demonstrated how menstrual cycles may synchronise as a result of the influence of female pheromones involved 29 women w a history of irregular periods samples of pheromones gathered from 9 women at different stages of cycle cotton pad in armpit worn for atleast 8 hrs pads treated w alcohol and frozen

findings

68% of women experienced changes to their cycle

limitation

P-commentators argue there are many factors that may effect change in a womens menstrual cycle-stress/diet E-these may act as confounding variables E-meaning that any supposed pattern of synchronisation is no more than would have been expected to occur by chance in addition

Point 2-evolutionary basis

P-menstrual synchrony is thought by many to have an evolutionary value E-for ancestors

Ultradian rhythms

A type of biological rhythm with a frequency of more than one cycle in 24 hours

stages brief

5 distinct stages of sleep that span approx 90 mins each stage is characterised by a different level of brainwave activity that can be monitored using an EEG

stage 1

light sleep muscle activity slows down brainwave patterns slower theta waves

stage 2

breathing pattern and heart rate slows alpha waves

stage 3

deep sleep begins slow delta waves w a greater amplitude

stage 4

rhythmic breathing very deep sleep delta waves

stage 5

brain activity speeds up and heart rate increases Rapid Eye Movement-REM denotes the fast activity of the eyes under eyelids REM is highly correlated w the experience of dreaming

stages 1-4

non REM

strength

P-evidence supports the idea of distinct stages in sleep E-researchers monitored the sleep patterns of 9 ppts in sleep lab brainwave activity recorded on EEG and researchers controlled for the effects of caffeine and alcohol E-REM activity during sleep was highly correlated w the experience of dreaming some of the ppts woken during dreaming reported very accurate recall of their dreams L-although small sample size in OG study was criticized by some-the study does suggest that REM sleep is an important component of ultradian sleep cycle

strength

P-some support for the importance of Basic Rest Activity Cycle from studies of elite performers E-Ericsson studied a group of elite violinists and found that