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Sleep and Biological Rhythms
Biological rhythms are patterns of physiological + psychological processes, repeated over a period of
time. Help animals measure time + enable them to anticipate and respond to change.
Circadian Rhythms bodily cycles that occur every 24 hourse.g. sleep/wake cycle.
Sleep/wake cycle is biologically determined + free running, meaning can run w/ out external cues,
typically set at 2425 hours.
+ve Miles Case study on male blind from birth, had no EZ but managed to maintain S/W cycle of
However, external cues needed, help internal clock adjust to environment.
+ve Aschoff + Weber placed pps in bunker, no natural light. Had S/W cycle of 2527 hours,
suggests EP can control S/W cycle w/ out EZ's, but light is necessary to coordinate biological rhythm
w/ external environment.
Evaluation of Circadian Rhythms
Ultradian Rhythms regular repeating pattern w/ a cycle that occur several times a day.
Numerous cycles that last around 90 minutes linked to medulla.
Rhythms begin early w/ Simunek and Sizen finding a rhythm of CNS activity (eye movement) begins
in foetuses as young as 20 weeks.
~Most common is sleep cycle, lasts 90 minutes each cycle + consists of 5 stages, the first 4 being NREM~
+ 5 being REM sleep
Stage 1 : Is light sleep, heart rate slows + temp drops. Brain waves become
slower going from alpha to beta .
Stage 2 : Waves slow down + have greater
frequency (theta waves)
Accompanied w/ sleep spindles + increase in amplitude (K complex)
Stage 3 + 4 : Is deep sleep or SWS, waves become delta, sleeper
unresponsive , metabolic rate reduce + growth hormone produced.
REM sleep : Sleep become lighter , goes back to stage 2 than REM.
Associated w/ dreaming , desynchronised EEG activity similar to awake
brain, rapid eye movements, body loses muscle tone (effectively paralysed)
Cycle continue w/ SWS period getting shorter + REM period getting
longer during night.
+ve Dement + Klietman : Monitored electrical activity using EEG + woke pps up when brain waves were
characteristic of REM sleep found 90% pps reported dreaming, but also found dreaming was reported in
NREM However has led to Neurobiological theories of dreaming making erroneous assumption that
REM sleep equals dreaming
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Infradian Rhythms bodily cycles that last longer than a daye.g. menstrual cycle.
Female menstrual cycle determined by release of oestrogen + progesterone under control of
pituitary gland (EP), function to regulate ovulation. (EP initiate + maintains rhythm)
Average cycle is 28 days , goes through 4 stages : menstrual phase, follicular phase, ovulation
phase + luteal phase.…read more