Sleep and Dreaming Flashcards
How many stages of sleep are there and how long for?
5 stages
each cycle of sleep is 90 mins
What happens in stage 1 of sleep?
light sleep can be easily woken muscles are less active eye movements slow twitch suddenly go through alpha and theta brainwaves
What happens in stage 2 of sleep
brainwaves are slower eye movement stops bursts of brain activity body temperature drops heart rate slows
What happens in stage 3 of sleep
deep sleep
slow delta waves
also some fast waves
this stage is in between light and deep
What happens in stage 4 of sleep?
deep sleep all waves are slow delta waves hard to wake you no eye movement can feel disorientated can experience night terrors or sleepwalking
What happens in REM sleep/what is it?
20% of sleep is REM for infants 50% is REM REM = rapid eye movement eyelids flicker quickly dreaming occurs sensory blockade neurons are shot off = movement inhibition rapid, shallow and irregular breathing eyes jerking muscles paralysed heart rate blood pressure rises stimulates increase of proteins some people report dreaming in NREM sleep, not always accurate
How long people need sleep for
adults = 7 or 8 hrs
teenagers = 9 hrs
age 65< = sleep stops, very sleep deprived so can’t perform functions well
What are circadian rhythms
human bodily rhythms
sleep-wake cycle
What are ultradian rhythms
rhythms that occur in <24 hrs
just sleep
Factors affecting the sleep-wake cycle
Jet lag = sleep-wake is triggered by light and time cues, different can cause irritability and poor concentration and tiredness
Shift work = different time cues affect biological rhythms
Internal influences on sleep
Hormones = sleep resets hormones
= can affect sleep because of stress, under stress ACTH releases cortisol, causing alertness -> hard to fall asleep
= people with insomnia produce too much cortisol/at wrong time
= melatonin signals need for sleep
= triggered by darkness
= synchronises circadian rhythms
=affects time of sleep
External influences on sleep
exogenous, environmental features: light, time cues, stress, eat and drink, medication
zeitgebers:
- regulate body’s circadian rhythm
- 12 month cycle
- mood and performance
- jet lag, shift work, light
- light lets internal body clock know whether its day or night = when to sleep
- body clock reset over 24 hr period
- entrainment =bodily rhythms matches to their environmental triggers -> light you are awake
Strengths and weaknesses of internal influences
+ hamster study = removed SCN from hamsters and sleep-wake patterns became random
+ human study of blind man = found his bodily rhythms are closer to 24hrs, circadian rhythms are governed by internal influences
+ Li-You Chen et al (2015) = melatonin controls sleep found in rats, sleep deprivation reduces melatonin levels -> melatonin reduces sleep
- animal studies cannot be generalised
- individual differences to being blind, hard to generalise to people who aren’t blind and without that specific blindness
Strengths and weaknesses of external influences
+ practical applications for understanding body clocks in humans = zeitgebers
+ Ralph and Skene agree that light synchronises bodily rhythms
- Siffre found the sleep-wake cycle could be 48 hours, studies differ
- situation of sleep-deprivation studies are not natural, lack validity
Name some sleep disorders of depression
Insomnia
Narcolepsy