PSYA3 Revision
BIOLOGICAL
RHYTHMS & SLEEP
Part 2: Sleep
Syllabus
Biological Rhythms
• Circadian, infradian, and ultradian rhthyms,
including the role of endogenous
pacemakers and of exogenous zeitgebers in the
control of circadian rhythms
• Disruption of biological rhythms, for example shift
work, jet lag
Sleep
• The nature of sleep including stages of sleep and
lifespan changes in sleep
• Functions of sleep, including evolutionary and
restoration explanations
Disorders of Sleep
• Explanations for sleep disorders, including
insomnia, sleep walking and
narcolepsy
NATURE OF SLEEP
• MUST BE ABLE TO
– Outline the different STAGES of sleep and say how
they are different (brain wave activity, bodily
changes)
– Explain how sleep changes across our LIFESPAN
• SHOULD BE ABLE TO
– Make reference to brief, general evaluative
comments
NATURE OF SLEEP
• 5 Stages
NREM
SLEEP
• 1: Theta waves make an appearance. Myoclonic
Jerks. Person is easy to wake
• 2: Theta Waves Dominate. Sleep Spindles and K
Complexes
SLOW
• 3: Delta Waves appear
WAVE
• 4: Deepest sleep. Dominated by delta waves.
(Deep)
SLEEP
Respiration rate lowest
• REM: Beta and Alpha waves (resembles being
awake). Dreaming. Rapid eye movement (linked to
dream content). Gradually extends in length each
cycle
• Sleep Staircase (1->2->3->4->3->2->REM… etc)
• Full cycle takes approx. 90minutes
Lifespan Changes
• OHAYON (2004) meta analysis of sleep studies found…
– Total sleep time decreases as we get older (470mins at age 5 ; 370
mins at age 70)
– Deep sleep (3&4) % decreases (25% -> 9%); may be linked to
restoration?
– REM sleep % decreases (25% -> 20%); may be linked to memory
consolidation?
– Adolescents sleep more at weekends and less during the week; may
highlight the influence of EZs on sleep?
• EVALUATION
– Objective measures used (e.g. brain scans)
– But as it is a meta analysis we cannot be sure ALL studies are
conducted under controlled, scientifically rigorous conditions; difficult
to compare results
– Individual differences need to be taken into account; careful not to
make nomothetic, deterministic conclusions
FUNCTION of Sleep
• MUST BE ABLE TO
– Discuss restoration theory of sleep
– Discuss evolutionary theory of sleep
Functions of Sleep - Restoration
AO1
• Sleep serves important
restorative functions
• NREM (especially slow
wave sleep) important
for bodily repair and
growth (release of
growth hormones,
protein synthesis etc)
• REM important for
neural (brain) repair and
growth (neurogenesis,
replenish
neurotransmitters, etc)
as well as cognitive
development (e.g.
memory consolidation)
AO2 / 3
• Evidence
– Case Studies of Sleep Deprivation (Tripp,
Gardner, Fatal Familial Syndrome)
• Ethical BUT have to be careful as they are case
studies (generalisation issues)
– Recthshaffen – Rats on a turntable – all
died!
• Ethical BUT problems with extrapolation
– Shapiro – Athletes sleep longer following
periods of exertion
– Ohayon – babies sleep for longer and have
more slow wave and REM sleep; makes
sense as babies are growing rapidly and
developing cognitive skills rapidly.
– Horne and Minard – CONTRADICTS; PPTS
did not sleep longer following periods of
exertion
Functions of Sleep - Restoration
General Evaluation
• Scientific and objective due to use of rigorous methods
• Biologically Reductionist – sleep serves other
important functions so we need to look at other
theories for a complete picture (e.g. evolutionary
theories – briefly outline)
• Individual Differences need to be taken into account
Functions of Sleep - Evolutionary
AO1
• Sleep is universal so it
must be ADAPTIVE
• Ecological Niches shape
the nature of sleep
• Sleep is adaptive because
it causes energy
conservation
• Sleep may protect animals
when they are most
vulnerable
• Sleep may be linked to
foraging (herbivores sleep
less because they need to
spend more time eating
to gain the required
nutrients)
• Sleep linked to predator –
prey status of the animal
(prey sleep less as they
are more vulnerable)
AO2 / 3
• Evidence from the ANIMAL KINGDOM (sloths, lions, sheep)
– BUT association NOT cause and effect
– Artificiality of animal studies as many are conducted in
controlled environments like zoos – does this reflect
‘normal’ sleep patterns
– Some exceptions (e.g. sloths)
•
Non reductionist theory – takes into account the whole animal
and their lifestyle instead of concentrating just on, say, physical
restoration.
– BUT does not allow us to identify the MOST IMPORTANT
factor which determines sleep patterns
•
•
•
Face Validity
Unfalsifiable due to the evolutionary nature of the theory
Alternative theories (e.g. restoration) should also be
considered to give us a complete / detailed view of the
function of sleep