Biological Rhythms Flashcards
what are biological rhythms
cyclical patterns within biological systems = evolved in response to environmental influences
names of the 2 factors that affect biological rhythms
- Endogenous pacemakers (internal)
- Exogenous zeitgebers (external)
types of biological rhythms, with examples
- circadian = last for around 24 hrs
e.g. sleep/wake cycle - ultradian = last less than 24 hrs
e.g. stages of sleep - infradian = lasts more than 24 hrs
e.g. menstrual cycle
what is the sleep/wake cycle, how does is work
body’s biological clock
- controlled by SCN (suprachiasmatic nuclei)
1. eyes detect light
2. send message to SCN, concerning brightness level
3. SCN use info to coordinate circadian rhythm activity along with homeostasis
4. if been awake for long time, homeostasis tells body there is need for sleep because of energy consumption
5. homeostatic drive for sleep increases throughout day, till reaches max at late evening = most people fall asleep.
factors that can affect sleep/wake cycle
exogenous
- light (natural/artificial)
- clocks
- jet lag
- shift work (night shift)
endogenous
- regulation of melatonin
- body temperature
- natural sleep drive
- homeostasis
outline Siffre’s research into the sleep/wake cycle (1975)
- spent 6 months in Texan cave, no exogenous zeitgebers, e.g. natural light/sound
- had no idea what time it was
- sleep/wake times, food = monitored
- sleep/waking cycle = erratic at first, then settled into fairly regular cycle of about 25 hours - slightly longer than the 24 hour day regular
pros and cons of research into circadian rhythms
PROS
= evidence for impact of external factors on sleep/wake cycle = inform how to improve sleep, e.g. no night shifts, avoid light before bed
CONS
= low generalisability
= could be argued that other factors = more important than light, more holistic approach may be more valuable
- Buhr et al found temp.; powerfully affects body clock
what are the stages of sleep
S1 & 2 (NREM)
= Light sleep = slower brain wave patterns, more rhythmic
- Alpha wave progression to theta waves
- Heart rate reduces
S3 & 4 (NREM)
= Deeper sleep = difficult to wake someone up
- Regular EEG patterns
S5 (REM)
= Rapid eye movement
- Dreaming
- Unique EEG activity = resemble awake state and mixture of brain waves (theta and alpha waves)
- Very hard to wake someone up
outline research into stages of sleep
Jouvet (1967) = lesioned raphe nucleus (a brain structure) in cats = found that resulted in sleeplessness
- also lesioned the locus coeruleus (another brain structure) resulted in loss of REM sleep
pros and cons of research into ultradian rhythms
PROS
- conducted in lab setting = high reliability and replicability, demonstrate causation
CONS
- animal study = cannot extrapolate
- artificial setting = not reflect natural sleep environment = low ecological validity
process of menstrual cycle
- approx. 28 days
- Regulated by hormones = promote ovulation or stimulate uterus for fertilisation
- ovulation = occurs halfway through cycle (oestrogen levels at highest) = 16-32hrs
outline research into menstrual cycles
McClintock = studied how pheromones impact menstrual cycle timing, rubbed upper lip of pps with pad of armpit odour of menstruating females
- found 68% of ppl experienced menstrual cycle changes = brought closer to ‘odour donor’
pros and cons of research into infradian rhythms
PROS
- provides insight that menstrual cycles (endogenous system) can be influenced by exogenous zeitgebers, e.g. other’s cycles
CONS
- confounding variables
e.g. stress, changes in diet, exercise
how does Siffre’s research provide evidence for circadian rhythms
- lack of exogenous zeitgebers in cave = found absence of external cues significantly alters circadian rhythm
