biological rhythms

biopsych

ultradian rhythms

biological rhythms that repeat throughout the day

what are examples of ultradian rhythms?

• sleep cycle

• hormonal release

• thermaregulation

• urination/bowel movements

infradian rhythms

biological rhythms that last longer than 24 hours

what are examples of infradian rhythms?

• menstruation

• breeding

• tidal rhythms

• seasonal rhythms

who studied menstruation?

stern & mcclintok

what did stern & mcclintok do?

• 29 women with irregular perios

• pheromones from cotton pads in 9 of their armpits

• worn for 8+ hours

• treated w alcohol + frozen

• day 1 pads given on day 1 experiment

what did stern & mcclintok find?

68% of women experience changes in cycle that brought them closer to the sweat donor

what are the strengths of research into the menstrual cycle?

• synchrony has evolutionary value - babies at same time - 1 could look after all - however, competition for best mate

what are the weaknesses of research into the menstrual cycle?

• confounding variables - stress, diet & exercise - failure to replicate and find synchrony

• based on animal pheromone studies - well researched e.g., sea urchins - not necessarily extrapolatable - not all organs

what other research is there into menstrual cycles?

• Reinberg - caves - cycle shortened from 28 to 25 days - suggests light affects cycle

• Russel et al - similar study to Stern & McClintock

what is seasonal affective disorder?

persistent low mood & lack of activity & interest that happens seasonally

when do most deaths occur?

january

what can be used to treat SAD?

light therapy

what is light therapy?

sitting by a light box for 30mins - 1hr in the morning

how does light therapy work?

encourages brain to reduce production of melatonin & increase serotonin

what are the benefits of light therapy?

works in up to 60% of individuals

what are the weaknesses of light therapy?

• Eastman - recorded a placebo effect - 30% - doubt on chemical influence

what are the stages of human sleep patterns?

• stage 1 + 2: light sleep

• stage 3 + 4: deep sleep

• stage 5: REM

what happens in stage 1 & 2?

• muscle activity slows down

• breathing pattern + heart rate slows

• slight decrease in body temp

what happens in stage 3 & 4?

• brain begins to generate delta waves

• rhythmic breathing

• limited muscle activity

• delta waves

what is REM?

dream sleep

what happens in REM?

• rapid eye movement

• brainwaves speed up

• dreaming occurs

• muscles relax

• heart rate increases

• shallow rapid bretahing

what is the human meal cycle?

where the appetite rises and falls due to food consumption

what happens in the eating cycle?

• eating = blood glucose + leptin increases, ghrelin decreases

• VMH turns off eating = satiety

• eating stops = blood glucose + leptin decreases, ghrelin increases

• LH turns on eating = hungry

what research has there been into sleep stages?

• Gardener - awake for 264 hours - slept for 15h after - recovered 25% of lost sleep over nights - recovered 70% deep sleep + 50% REM - high degree of flexibility

• Tucker et al - individual diff between pps during each stage - duration

what did Dement & Kleitman do?

• monitored sleep patterns

• 9 adults

• EEG

• sleep lab

• controlled caffeine + alcohol

what did Dement & Kleitman find?

• REM highly correlated w dreaming

• brain activity varied with vividity

• accurate recall when awoken

what is the basic rest activity cycle?

the 90 min cycle found during sleep also occurs throughout the day

what anecdotal support is there for the basic rest activity cycle?

• frequent observation of students finding it difficult to concentrate longer than 90 mins

• most people require breaks to divide morning

• best performers tend to practice for 3 sessions less than 90 mins + with breaks