biological rhythms Flashcards
what’re the 3 different biological rhythms
circadium rhythm (occurs once every 24hr)
infradian rhythm (takes >24hr to complete, more than a day)
ultradian rhythms (<24hr to complete, less than a day)
what’re 2 key circadian rhythms
sleep/wake cycle
core body temperature
what’s the sleep/wake cycle
melatonin peak - 9pm
melatonin trough - 7:30am
what is melatonin
a hormone produced by the brain in response to darkness involving the sleep/wake in circadian cycle rhythm
when is the core body temperature cycle
~6pm highest body temperature
~4am lowest body temperature
what was Folkard’s study of natural biological rhythms
participants lived in a cage for 3 weeks required to sleep from 11:45pm-7:45am. however the experimenters gradually sped up the clock so that 24hrs passed in 22hrs. the participants were unable to adjust, showing how our endogenous pacemakers are dominant over our exogenous zeitgebers
what’re biological rhythms
patterns of changes in body activity that conform to cyclical time periods.
what influence biological rhythms
internal body clocks (endogenous pacemakers)
external environmental changes (exogenous zeitgebers)
(can be either or both)
what was was Aschoff & Wever’s study
participants spent 4 weeks in a ww1 bunker, deprived of natural light. almost all patients had a circadian rhythm of 24-25 hours. shows how usual free-running circadian rhythm is just over 24hrs long however normal day-to-day life is restricted to 24 hours due to exogenous zeitbegers) eg meal times/daylight
what does evidence suggest about core body temperature
the warmer we are (internally) the better our cognitive abilities,
Collard found children who read stories at 3pm had greater recall/comprehension than those who read stories at 9am
2 positive evaluations of circadian rhythms
night shift
medical treatments
2 negative evaluations of circadian rhythms
individual differences
unrepresentative participants
what positive evaluation on circadian rhythms can be seen from night shifts
night shift workers have reduced concentration at ~6am, meaning accidents and mistakes are more likely, also night shift workers are 3x more likely to develop heart disease. therefore, companies can better care for the well-being/productivity of their night shift workers e.g. light/breaks
what negative evaluation on circadian rhythms can be seen from unrepresentative participants
participants must agree to prolonged periods of time in caves for circadium rhythm studies, making a small and unrepresentative sample size. this has low generalisability due to participants being of certain demographics ie unemployed, introverted, students, or psychological enthusiasts, making the studies less generalisable
what negative evaluation of circadian rhythms can be seen from individual differences
some people have sleep/wake cycle differences from 13-65 hours (larks and owls), with age differences also. as a result the data has low applicability due to the vast number of individual differences amongst the population
what positive evaluation of circadian rhythms can be seen from medical treatments
the body’s basic processes eg heart rate change within a 24hr period, leading to “chronotheraputics” - research into how medicines can be administered at the most effective times of day eg if aspirin is taken at night rather than day then it’s more effective as a treatment for heart disease. this is a strength as it has allowed for better/faster recoveries better benefiting society
summarise the 5 cyclical processes that occur during a menstrual cycle
•~28 day regularity
•ovulation occurs halfway (14 days)
•ovulation occurs at peak oestrogen levels
•after ovulation, progesterone levels increase to rebuild uterus lining
•processes regulated by the ovaries
what was McClintock’s study
took 29 women with irregular periods, 9 of which gave pheromone samples at various stages of the menstrual cycle by wearing a cotton pad in the armpit for 8 hours, later rubbed on the top lips of the 20 women. repeated each day. inspired by the finding that women who spent extended time together in uni halls often synchronised their menstrual cycles
what’re the McClintock results
68% experienced cycle changes that brought them closer to their ‘odour donor’
what is Seasonal Affective Disorder (SAD)
common infradian rhythm, a kind of depression which seems to occur on a seasonal basis, with ~11,000,000 US sufferers
where does SAD most commonly occur
North, eg in Florida (far South) ~1.4% of the population, Maine (far North) has as high as 10%
why does SAD thought to occur
in more Northern latitudes there is decreased amounts of daylight in winter, causing melatonin to be secreted for longer periods of time due to the lack of light, thought to have an effect on serotonin and creating depressive symptoms
what’re 2 positive evaluations of infradian rhythms
evolutionary basis
practical applications in the form of treatments
what’s a negative evaluation for infradian rhythms
many confounding variables in McClintock’s study as many factors effect menstrual cycle eg stressed diet and exercise. therefore difficult to establish cause-and-effect and lowers internal validity. furthermore the sample size of 29 women is small and other similar studies have failed to find evidence of menstrual synchrony in female samples
how is evolution a positive evaluation for infradian rhythms
if females have birth at the same time then new-borns could be cared for collectively, increasing survivability chances, for example if a mother dies in pregnancy then the child will still have access to breast milk
how is applications of infradian rhythms (SAD) a positive evaluation
new treatments have been developed, eg light therapy with a strong light box that relieves symptoms in ~80% of sufferers of SAD. strong light is said to reset melatonin levels which resets the body’s internal clock. whilst light therapy is light/effective it can cause headaches and eye strain. However, relapse rates have been recorded at 46% with light therapy and only 27% with CBT
what’re ultradian rhythms
frequency of more than once every 24 hours, the stages of sleep
how long do the 5 distinct sleep stages span altogether
~90 minutes
what’re characteristics of the 1st stage of sleep
~5 minutes, change from wake to sleep, follows REM, alpha waves, muscles relax/often twitch
what’re characteristics of the 2nd sleep cycle
40-50 minutes, light sleep, breathing/heart rate slow, slight body temp decrease, ~half of your sleep, alpha waves
what’re characteristics of the 3rd/4th sleep cycle
15-20 minutes, deep sleep begins to move to very deep sleep, breathing/heart rate slow, limited muscle activity, hard to wake, delta brain waves
what’re characteristics of the 5th sleep cycle
REM, brain is very active with theta waves, dreams, heart rate/bloody pressure increase, body/muscles often inactive - maybe ‘sleep paralysis’
how do the sleep cycles work
the more sleep cycles completed the less deep sleep needed and more time spent alternating from light and REM sleep
what’s a positive evaluation of ultradian rhythms
helps better understand age related sleep changes, SWS (slow wave speed) reduces with age, growth hormone usually produced during SWS, may explain issues eg reduced alertness, relaxation techniques or medication can be prescribed and helps ensure better SWS among elderly
what’s a negative evaluation of ultradian rhythms
sleep labs and EEG’s are used, very unrealistic, leads to non-generalisable results with low internal validity
