Endogenous Pacemakers & Exogenous Zeitgebers Flashcards
What is an infradian rhythm? + an e.g.
A type of biological rhythm with a frequency of less than one cycle in 24 hours, e.g. menstruation and seasonal affective disorder
Outline the menstrual cycle - an infradian rhythm
Governed by monthly changes in hormone levels - the cycle is the time between one period and the next - typical cycle is 28 days - in each cycle oestrogen increases causing an egg to release - then progesterone helps thicken the womb lining - if not pregnant egg absorbed into body and womb lining leaves the body
Outline some research into infradian cycles?
Stern and McClintock (1998) Took pheromone samples from women on their menstrual cycles (at different stages) and passed them onto other women -68% experienced changes to their cycle that brought them closer to the pheromone donor. The menstrual cycle is an endogenous system but evidence suggests that it may be influenced by external factors
What is seasonal affective disorder?
A depressive disorder which has a seasonal pattern of onset
What are SAD’s characteristics?
It’s characterised by low mood, activity and interest in life –‘winter blues’
What type of biological rhythm is SAD and what causes it?
A particular type of infradian rhythm called a circannual rhythm bc its yearly but also circadian bc SAD may be caused by disruption to the sleep/wake cycle bc of changing day lengths. Possible that melatonin is implicated - during winter the production of melatonin continues for longer due to lack of light in the mornings – knock on effects for serotonin production in brain – associated with depressive disorders
What is an ultradian rhythm? + an e.g.
A type of biological rhythm with a frequency of more than one cycle in 24 hours, such as the stages of sleep
What are the stages of sleep?
Psychologists have identified five stages of sleep that span approximately 90 minutes - the cycle continues throughout the night - each stage is characterised by different levels of brainwave activity
1 and 2. The sleep escalator - light sleep - brainwave patterns start to become slower and more rhythmic (alpha waves) as sleep becomes still deeper theta waves occur
3 and 4. Deep sleep or slow wave sleep - involve delta waves - slower still and have a greater amplitude
5. REM sleep - body paralysed - brain activity speeds up - rapid eye movements, fast jerky activity of eyes under eyelids - highly correlated with experience of dreaming
Explain why the menstrual cycle is said to have an evolutionary bias (Eval -)
Evolutionary value for females to fall pregnant together – newborns cared for collectively in a group – increased chance of survival – maybe not bc of biological rhythms ..
BUT; Schank (2004) said it wouldn’t be advantageous bc of competition for best quality males
What were the methodological limitations of synchronization studies? (Eval -)
Many confounding variables weren’t controlled during the study, such as stress, diet, exercise, etc. Typically these studies are carried out on small groups of women who self report the findings. Other studies have even failed to find any form of synchrony in all female samples
What evidence supports the idea of distinct stages in sleep? (Eval +)
William Dement and Nathaniel Keitman (1957) – monitored sleep patterns of 9 adult pcps – brainwaves recorded on EEG – controlled for effects of caffeine/alcohol – REM activity highly correlated to dreams – if woken during dream, better recall of it
Animal studies are used to investigate ultradian rhythms (Eval -)
The fact that we know animals release pheromones to contact other animals is well documented. Evidence for the effects of pheromones in humans is still inconclusive and largely speculative
