Introduction to sleep Flashcards
Define sleep
A condition of the body and mind which lasts for several hours each night, occurring cyclically
Where the nervous system is inactive, eyes closed, postural muscles relaxed and consciousness suspended
Define unihemispheric sleep
This occurs to certain mammals that have uncoupled the hemispheres of their brain e.g., dolphins, enabling half their brain to sleep whilst the other hemisphere is active to enable movement in water
(also occurs in birds)
What are the 4 sleep theories?
Evolution, brain plasticity, restoration & energy conservation
Explain evolutionary theory regarding sleep
The inactivity during the night has been proposed to be an adaptation vital for survival. As staying quiet, still-moving & overall inactive proves an advantage of not creating attention that could draw in predators
-reduced predation
-reduced accidents in dark
-reduced exposure to threat
(if sleep wasn’t important animals would have adapted to survive without it)
Explain the energy conservation theory
The theory is that sleep occurs to limit energy expenditure as sleep provides rest and inactivity
This decreases the demand on the body.
e.g., hibernation in bears
Explain the brain plasticity theory
This theory suggests that there is a correlation between brain structure & organization of the brain regarding to sleep
Sleep is seen as essential for the brains ability to perform tasks & to learn.
Explain the restoration theory
This theory suggests we sleep in order to undergo growth, repair & restoration.
We are more likely to deal with illness & injury when sleep-deprived.
Sleep deprivation causes a reduction in immune efficiency
Tissue growth & repair occur during sleep, rate of protein synthesis & cell division increase during sleep
The hormone of HGH is released during NREM sleep
Define NREM
Known as non-eye rapid movement sleep, which is required for restoration of physical function, HGH released during NREM
Define REM
Known as rapid eye movement sleep, which is needed to restore brain function, there is an increase in REM sleep during sleep deprivation. Brain repair cannot occur when conscious
How is sleep measured?
Measured by an EEG, involves electrodes placed on the scalp to measure different types of waves & record the electrical activity of the brain. This is used to identify sleep stages, patterns & abnormalities
What is the function of the glymphatic system
This system drains toxins from the brain, similar to the lymphatic system, however, this system is 10-20 more times active during sleep
Glial cells found in the brain shrink allowing large gaps between neurons, enabling cerebral fluid to flush out toxins
What is the effect of sleep on memory?
It is known sleep deprivation affects cognitive function
Memory consolidation (STM->LTM) cannot occur whilst awake due to environmental demands
REM is very important for memory consolidation, found slow wave sleep & REM are vital
What are the types of sleep waves & how are they measured?
Waves are measured by amplitude, frequency & wavelength
(1Hz=1 wave/s)
infraslow=<0.5
Delta=0.5-3.0
Theta=3.0-8.0
Alpha=8.0-12.0
Beta=12.0-38.0
Gamma=38.0-42.0
What are the 3 stages of NREM sleep?
- transition from wakefulness to sleep
- first sleep stage
- slow wave sleep (SWS)
Describe events occurring in S1 of NREM
Occurs in first 10 minutes, 2-5% of time spent in this stage
- body muscles are still functioning, eye-rolling occurs, waking in this stage makes us feel we have not slept at all
-HR & BR begins to slow, BP & temperature decreases,
-hypnogogic jerk (falling sensation)
Describe events occurring in S2 of NREM
Lasts approx for 10-25 minutes, and lengthens with each successful sleep cycle, spend 45-55% of sleep in this stage (light sleep)
- HR, & body temp drops
- metabolism slows
- harder to wake up from, conscious awareness decreased
- if woken, are aware we have slept
- Theta waves are present between 12-14 Hz
- K-complex occurs
Describe events occurring in S3 of NREM
Lasts for 40 minutes, occurs 35-45 mins after first falling asleep
15-20% time spent in this stage
- has delta waves & sleep spindles
- BP, HR, BR & temp are at lowest levels
- sleep will continue through disturbances, heavy sleep
- If woken leads to disorientation
- Dreaming may occur as well as parasomnia (e.g., sleepwalking/ bed-wetting)
- Information processing and memory consolidation occur
- Children & young infants have more of this sleep than adults
What is the K-complex
Occurs during S2 of NREM
K-complexes consist of a brief high-voltage negative signal, followed by a slow positive and then a high negative peak
They are proposed to protect sleep, enable memory consolidation, suppress stimuli and support information processing.
Describe events that occur during REM sleep
REM lasts for 10 minutes, takes 1.5hrs to occur after falling asleep, REM increases with each successful sleep cycle.
Infants spend 80% time in REM, adults spend 20%
- involves rapid eye movement
- skeletal muscles are paralyzed to prevent acting out of dreams
- vivid & emotional dreams occur
- HR, BR & BP become irregular
- Core temp is poorly regulated
- REM sleep waves have low amplitude, mixed frequencies, different waves of theta, alpha & beta waves
-Have a saw tooth pattern
-Paradoxical waves look like brain waves when awake, has some sleep spindles
Define sleep paralysis
A sleep disorder that causes people to wakeup during REM, are paralyzed, unable to move or speak. May experience hallucinations
What is recommended hours of sleep for adults & infants?
Adults-8hrs minimum
Children-14-16hrs
What is causing the world to become more sleep deprived?
- Artificial lighting from technology affecting circadian rhythms
- Blue light from technology
- Work and shift patterns
- Early school starts
- 24/7 entertainment available
What are the consequences of sleep deprivation?
- Reduced memory consolidation
- reduced concentration
- reduced motor function
- reduced cognitive function
- poor dietary intake (drawn to food high in sugar, carbs & fat)
- reduced immune system
- increased risk of anxiety, stress & depression
- reduced sex drive
- increase risk of accidents, injury and mistakes
What is the correlation between car accidents & sleep deprivation?
20% of accidents in cars are caused by sleep deprivation
Peak times are early morning and post-lunch slump
Men under 30 are at the highest risk of falling asleep behind the wheel
Leading to injury/fatality
Define sleep hygiene
The behaviors we carry out before bed that promote sleep
Give examples of good sleep hygiene (give at least 5)
- Going to bed & waking up at the same time every day
- Not eating a large meal before bed
- Setting a bedtime for a minimum of 7 hours of sleep
- Not hitting snooze
- Not napping in the day
- going to bed only when tired
- make sure the bedroom is quiet, dark & comfortable
- make sure bed is only used for sex & sleep
Give examples of poor sleep hygiene (give at least 5)
- Clock watching
- stimulants such as nicotine, caffeine or alcohol
- eating or drinking large amounts before bed
- avoid exercise a few hrs. before bed, as endorphins inhibit sleep
-Technology before bed, blue light inhibits melatonin production
Explain Caffeine inhibition on sleep
Caffeine blocks adenosine receptors in the brain, reducing sleep, if adenosine accumulates, sleep will not happen
Caffeine has a half-life of 6 hrs, afterwards a caffeine crash occurs
How do we investigate sleep?
In recent years study into sleep has been increasing, with more sleep disorders being identified, it has been found that those with obesity tend to suffer with sleep apnoea
How can we investigate sleep:
Sleep diary (keep for 2 weeks, notice sleep patterns and hygiene)
Patient history
Sleep study (actigraphy and overnight oximetry)
Sleep recording
Polysomnography
