Sleep Flashcards
What is a circadian rhythm?
variation in physiological processes that cycles in a ~24 hour period
What are some physiological changes that follow a circadian rhythm?
body temperature, melatonin levels, alertness
What rhythm is followed by people when left in the absence of time cues?
free-running rhythms
Why don’t humans usually free-run?
time cues (sunlight, alarm clock) reset our internal clock every day
What is an ultradian rhythm?
a cycle that lasts less than 24 hours
What type of rhythm do sleep stages follow?
ultradian
How do typical free-running rhythms compare to circadian rhythms?
free-running rhythms are slightly longer
What do EEG readings indicate during sleep?
changes in brain activity
What waves do EEG scans show when someone is awake?
beta waves
When do EEG scans show alpha waves?
when awake but relaxed and drowsy
How many stages make up non-REM sleep?
4
What brain waves are seen in non-REM sleep?
theta and delta
What brain waves are seen during REM sleep?
beta-like waves
What are the characteristics of beta waves?
rapid, low-energy waves?
How do alpha waves compare to beta waves?
slower
How do theta waves compare to alpha waves?
slower, lower energy
What characteristics does REM sleep share with wakefulness?
- increased heart rate, blood pressure, respiration
- muscle twitching (fingers and face)
- eyes move around (under lids)
What is muscle tension during REM sleep?
very relaxed - almost paralyzed
Why might it be a benefit for muscle tension to be relaxed during REM sleep?
to prevent injury from acting out dreams
What happens when a person first enters stage 1 sleep?
- brain changes to theta waves
- become less responsive to outside world
How much is needed to wake up someone in stage 1 sleep vs. a later stage?
not much needed to wake up from stage 1
What brain waves dominate stage 2 sleep?
theta waves
What stages of sleep are dominated by delta waves?
stages 3 and 4
What happens after reaching stage 4 sleep for the first time?
brain transitions back to stage 1, where REM sleep occurs
How many sleep cycles does an adult have during a typical night?
4-6 cycles
How does the length of REM sleep change as more sleep cycles are completed in one night?
it lengthens
How does the amount of time spent in non-REM sleep as a night progresses?
it decreases
What is the acoustic arousal threshold?
amount of sound required for awakening
What is used to characterize sleep depth?
acoustic arousal threshold and EEG
How does the time spent in REM sleep change over a lifetime?
time spent in REM decreases sharply from birth and childhood, continuing to trop as we age
How does the time spent in non-REM sleep change as we age?
decreases slightly
What is a possible reason to explain why children spend more time in REM sleep than adults?
REM sleep assists in brain growth and development
How does sleep structure vary between long sleepers (>8.5 hours) and short sleepers (<6.5 hours)?
long sleepers spend more time in REM/stage 1 and 2 sleep than short sleepers, whereas stage 3/4 sleep time doesn’t change
What happens to sleep deprived organisms?
physical deterioration, inhibited neural growth, impaired memory
What is the restoration theory of sleep?
sleep is necessary for physical restoration of cells in body
How does the body get damaged during the day?
oxygen metabolism produces harmfull free radicals in cells
How can sleep repair physical damage?
produces enzymes to fight cell damage
What is some support for the restoration theory?
sleep deprivation leads to breakdown of tissues; sleep more after a marathon
How did sleep structure vary between control groups and people who exercised 30 minutes or 60 minutes at their maximum intensity threshold?
it was mostly preserved - only a minor difference in stage 1 sleep (less time spent in stage 1 for those who exercised)
What does WASO stand for?
wake after sleep onset
How did WASO vary between controls and people who exercised 30 or 60 minutes?
WASO was lower for those who exercised
What are two measures of sleep quality?
WASO (wake after sleep onset) and latency
What is sleep latency?
the length of time it takes to fall asleep
How long does it usually take to fall asleep?
15-20 minutes
What is the memory consolidation theory?
sleep enhances learning and memory
According to the memory consolidation theory, what does the brain do during sleep?
rehearses new tasks (hippocampus activity seen when learning something is repeated during slow-wave sleep - neurons fire in same pattern)
What is some support for the memory consolidation theory?
sleep architecture changes with learning, and sleep deprivation reduces learning improvement
How does sleep architecture change after learning something new?
increased REM sleep
How does improvement in learning a task relate to sleep?
less sleep, less improvement
What effect does chronic sleep restriction have on cognitive function?
it produces cognitive impairments
What does 4 hours of sleep restriction per night over two weeks correspond to?
2 days of total sleep deprivation
What is sleep debt?
the amount of sleep our brain owes our body
How does sleep debt get paid back?
by increases in slow wave sleep (not total sleep time)
How does sleep restriction to 4/6 hours a night differ from total sleep deprivation in terms of sleepiness ratings over time?
sleepiness increases very sharply for total deprivaiton while it gradually increases over time for 4/6 hours
How does sleep architecture change when sleep is restricted?
slow wave sleep time stays constant, while stages 1 and 2 time are decreased
What are some signs of sleep deprivation?
needing an alarm clock to wake, sleeping longer on weekends, falling asleep during lectures
What are insomnia, sleep apnea, sleepwalking, narcolepsy, and hypersomnia?
sleep disorders
What is insomnia?
sleep difficulty characterized by difficulty falling and staying asleep, as well as not feeling rested
What are some possible causes of insomnia?
restless leg syndrome, erratic hours, medical conditions, psychological disorders, alcohol/drug use, iron deficiency
How can insomnia be treated?
increase effect of GABA
How does increasing GABA’s effect help treat insomnia?
it decreases CNS activity, producing a general feeling of relaxation
What is the problem with treating insomnia with GABA?
the brain can adapt to GABA’s inhibitory effects by making neurons less excitable, which causes rebound insomnia when drug use is stopped
What is sleep apnea?
sleep difficulty that ersults from temporary blockage of air passage
What sleep disorder is more common in men and obese people?
sleep apnea
How does sleep apnea affect one’s sleep structure?
lack of deep sleep and REM sleep - sleep deprived
What sleep disorder increases the risk of car accidents, diabetes, and heart disease
sleep apnea
How can sleep apnea be treated?
weight loss, surgery, devices that keep throat open
What is sleepwalking?
sleep difficulty characterized by activities occurring during non-REM sleep that usually occur when awake
Why can’t sleepwalking occur during REM sleep?
muscle activity is inhibited during REM
What sleep disorder is more common in children?
sleepwalking
What is narcolepsy?
sleep disorder characterized by excessive daytime sleepiness and weakness in facial and limb muscles
What is a term to describe a weakness in facial and limb muscles?
cataplexy
What does a defecit of orexin cause?
narcolepsy
What is orexin?
neurotransmitter important for arousal
What sleep disorder has a genetic basis and why?
narcolepsy - caused by lack of orexin
What are amphetamines and antidepressants used to treat, and what aspects of the disorder do they deal with?
narcolepsy; amphetamines help prevent daytime sleepiness and antidepressants help with cataplexy
What is hypersomnia?
sleep difficulty characterized by sleeping more than 10 horus a day for 2+ weeks, including the urge to nap during inappropriate times
What can apnea, brain injury, and/or depression cause?
hypersomnia
What sleep disorder is correlated with suicidal adolescents?
hypersomnia
What are dreams?
images, thoughts, and feelings experienced during sleep
What dream theory states that dreams are “the royal road to the unconscious?
Freud’s psychoanalytic theory
What are the two levels of access of dreams, according to Freud?
manifest level and latent level
What is the manifest level of dreams?
what you actually dream - the surface level, recalled upon waking
What is the latent level of dreams?
the deeper unconscious level, where true meaning lies
What does Freud think the latent level of dreams reveals?
hidden conflicts
What evidence does the memory consolidation theory present to indicate that dreaming (REM) supports memory functions?
new learning increases amount of REM, while REM deprivation impairs certain types of memory and synaptic plasticity
Other than REM, what is important for some types of learning?
non-REM sleep
What role does the suprachiasmatic nucleus (SCN) play?
internal timekeeper - regulates physiological activity on daily cycles
Where is the suprachiasmatic nucleus located?
hypothalamus
What structure keeps the body’s circadian rhythms on track?
SCN
How does the SCN regulate alertness in the morning?
- retina in eye senses morning light
- stimulates SCN
- sends signals to pineal gland to decrease amount of melatonin levels released
How does the SCN regulate alertness in the evening?
- SCN activity decreases
- more melatonin secreted
- increased relaxation
What is melatonin?
hormone with role in relaxation/drowsiness
What can melatonin be taken to combat?
jet lag
What neurotransmitter is found in neurons in the basal forebrain?
acetylcholine
What effect does acetylcholine have on the brain in regards to sleep?
produces rapid EEG activation patterns observed in waking and REM sleep
Do neurons in the preoptic area promote or inhibit sleep and what neurotransmitters do they contain?
promote sleep (GABA)
What part of the brain contains orexin neurons?
posterior hypothalamus
