3) Lasts 15 mins. EEG activity is characterised
by long slow- delta waves with sleep spindles.
4) Lasts 30 mins approx. Slow - wave sleep- long slow waves
of EEG. The EOG & EMG show very little activity.
5) Lasts approx 10 mins- first cycle -builds up to an
hour by 4th/5th cycle. EEG activity is characterised by
beta waves- relaxed waking state linked to dreaming.
Circadian Rhythm
Lasts about 24 hours e.g. Sleep wake cycle, Body temp
1) Humans and mammals have an
endogenous pacemakers - internal
biological - suprachiasmatic nucleus
(SCN) -lies in the hypothalamus -lies
above optic nerve.
2) SCN sends signals to pineal
gland-increase production melatonin at
night- Melatonin induces sleep
inhibiting brain mechanisms that
promote wakefulness
Infradian Rhythm
Occurs for a period more than one
day but less than one year e.g. Female
Menstrual Cycle- lasts approx 28 days
Female Menstrual Cycle (AO1)
Driven by fluctuating hormone
levels. Research suggests - pituitary
gland releases hormones which
stimulate follicle in 1 ovary to ripen
egg- release oestrogen
SAD (AO1)
Infradian rhythms do not have to
monthly- can occur once a yr. SAD can
occur e.g. during winter months and
people recover in the summer.
Research shows- melatonin secreted -pineal gland =
dark ; more darkness - the more melatonin. Research
also shown- melatonin related to chronic depression.
But SAD may be due- disruption to circadian rhythm
e.g. go to bed earlier wake up later in dark
Circannual Rhythm
Occurs or fluctuates at
intervals of approx one year
e.g. Migration of birds
What controls Biological Rhythms?
Endogenous Pacemakers- Regulate your rhythms inside your body
Exogenous Zeitgebers- Regulate your behaviour outside your body
Disruption of biological rhythms
Shift Work
- Decreased alertness - sleep deprivation -
effects on health
Jet Lag
Erroneous decision making - hard to
make decisions due to jet lag.
Less difficulty - travelling east to west (phase delay)
More difficulty to adjust West to East (Phase Advance)
Real life applications: IDA
Chernobyl, Exxon Valdez oil tanker grounding, space shuttle challenger