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)