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BIOLOGICAL RHYTHMS AND SLEEP

1) CIRCADIAN RHYTHMS

Ao1 ­ Sleep Wake Cycle

Circadian = 24 hour cycle

External cues (sunlight, knowing time) guide circadian rhythm.

Internal endo clock is free running (works w/o external cues), sets cycle of 24-25hrs, ext cues just
help adjust it

Research ­ circ rhythm persists…

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2) INFRADIAN + ULTRADIAN RHYTHMS

Ao1 ­ Infradian Rhythms (more than 24 hours, less than year)

EXAMPLE ­ FEMALE MENSTRUAL CYCLE (regulates ovulation)

Pituitary gland releases FSH + LH ­ stimulate a follicle in ovary to ripen an egg, triggers release of
oestrogen. --> Once egg ripened, ruptured follicle releases…

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BRAC important - ensures bio process work in unison. ORCHESTRATES METABOLIC PROCESSES

3) ENDOGENOUS PACEMAKERS + EXOGENOUS ZEITGEBERS

Ao1 ­ Endogenous Pacemakers

SCN (Suprachiasmatic nucleus) in Hypothalamus is main one in mammals

SCN gets info from eye about light via optic nerve, even when eyes closed as light penetrates
eyelids…

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4) DISRUPTION OF BIOLOGICAL RHYTHMS

Ao1 ­ Shift Work and Shift Lag

Nightworkers experience trough of decreased alertness during shifts between midnight and 4am
(cortisol levels and body temp lowest) BOIVIN ET AL

Sleep deprivation experience as finish work during day. Daytime sleep difficult due to other factors
(noise). Daytime…

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Social customs (eating and sleeping at correct times) help too

Individual differences exist in coping with disruption ­ some not as badly affected as others

5) THE NATURE OF SLEEP AND LIFESPAN CHANGES

Ao1 ­ Babies and Children

Babies sleep for approx 16 hrs a day, non-continuously, wake up every…

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Childhood parasomnias rare but other disorders (insomnia + apnoea) more common

Old age ­ sleep time remains same but more difficulty so wake more during night, naps during day to
satisfy needs

Time in REM decreases to about 20% and SWS reduces to 5%, with other non-REM sleep increasing

Experience…

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6) FUNCTIONS OF SLEEP ­ RESTORATION EXPLANATIONS

Ao1 ­ SWS

SWS in stages 3+4 of non-REM sleep

Growth Hormone (GH) secreted during SWS. Decline in production of GH in older age due to reduced
total SWS, and so this lack of SWS can lead to poor immune functioning

Ao1 ­…

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7) FUNCTIONS OF SLEEP ­ EVOLUTIONARY EXPLANATIONS

Ao1 ­ Energy Conservation (WEBB)

Sleep provides a period of inactivity to conserve energy, which is essential for animals with high
metabolic rates (smaller animals, warm blooded)

Ao1 ­ Foraging

Herbivores spend less time sleeping, carnivores spend longer as their food full of…

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8) SLEEP DISORDERS ­ EXPLANATIONS FOR INSOMNIA

Ao1 ­ Short Term Insomnia

May be due to immediate worries (e.g. exams/death in the family, noises at night or jet lag)

Ao1 ­ Long term Insomnia

Primary insomnia ­ not associated with any medical condition (So due to bad sleep habits)

The…

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9) EXPLANATIONS OF OTHER SLEEP DISORDERS

Ao1 ­ Narcolepsy

Early approach suggested that sudden attacks of sleepiness disguise sexual fantasies

REM HYPOTHESIS - 1960s explanation was that it was due to malfunctions in the regulation of REM, as
they have abnormal REM sleep, similar to loss of muscle tone which…

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