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Importance of Sleep (Sleep Disturbances (Definitions (Sleep disturbance:…
Importance of Sleep
Sleep Disturbances
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Parasomnias
Sleepwalking (somnambulism) involves walking whilst asleep and sometimes conducting routine activities.
Most commonly observed in children but can also occur in adults (usually at times of high stress).
Occurs in stage 3 or 4 of NREM sleep and can go on for up to half an hour (Usually between 5 and 15 minutes).
Effects on sleep-wake cycle:
Loss of deep sleep (SWS and occasionally REM are interrupted).
Sleep episode is fragmented
Sleep deprivation may occur during NWC
Dysomnias
Insomnia is a problem which involves continually getting insufficient sleep.
A failure to fall asleep within 30 minutes after intended time.
Difficulty occurs at least 3 times per week
Sleep difficulty despite adequate opportunity to sleep
Awakening for more than 30 minutes during the night.
A complaint of poor sleep.
Feeling tired during the day
Effects on sleep-wake cycle:
Sleep deprivation causes a sleep debt to accrue through the week
Effects of sleep deprivation may occur during NWC. The cumulative effects can be potentially hazardous to health and wellbeing.
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Circadian Phase Disorder
Sleep disruption due to alteration of the internal circadian rhythm.
Can be characterised by an inability to fall asleep or to remain asleep
Mismatch between sleep-wake cycle & life schedule.
Mismatch between sleep-wake cycle & environment.
Bright Light Therapy
Treatment for circadian-rhythm disorders (i.e. sleep-wake cycle shift in adolescents, shift work & jetlag)
Used to reset the body’s internal clock gradually.
During light therapy your eyes are exposed to intense but safe amounts of light (light box) for a specific and regular length of time as artificial light may be used to affect the body clock in the same way that sunlight does.
Ages
Babies
REM VS NON REM 50/50
Sleep onset can occur at any time of the day
Fewer sleep cycles
Irregular/shorter duration of sleep cycle
As age increases, spend less time in total sleep and REM"
Teenagers - Adults
REM VS NON REM 20/80
Time spent in stage 2 increases
First REM period unlikely to be missed"
Elderly
REM VS NON REM 15/85
"More time spent in NREM as REM decreases
Overall time spent asleep decreases"
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Rhythms
Circadian – bodily changes that occur as part of a cycle with a duration of 24 hours.
Sleep-wake cycle
Environmental cues
It is determined by an internal body clock located in the hypothalamus.
This clock also regulates our level of arousal, metabolism, body temperature and hormone secretions.
Light is the main environmental cue
This then leads to melatonin being released
Ultradian - bodily changes that occur as part of a cycle with a duration of less than 24 hours.
Heartbeat
Respiration
Hunger
Hormone secretion
Alertness
Sleep
REM: Rapid eye movement
NREM: Non-rapid eye movement
Each type of sleep is characteristically different and has contrasting features and functions.
Special features:
Hypnogocic state
Hypnic jerk
Sleep spindle
K complex
Slow wave sleep
Hypnopompic state
80% of sleep is spent in NREM
As the night progresses time spent in NREM decreases
NREM is typically associated with physical restoration of the brain and body’s resources eg new brain and muscle cells created
NREM consists of 4 stages that range from light sleep to deep sleep
20% of sleep is spent in REM
Begins approximately 1/12 hours after sleep onset and increases as the night progresses
Characterised by rapid eye movement and a loss of muscle tone, the brain is showing a high level of activity while the body remains inactive (to the point of paralysis) Nerve impulses below the neck are blocked in order to stop us acting out our dreams
REM sleep is often referred to as paradoxical sleep because of the brains activity and the body’s inactivity- it’s a paradox !
Theories
Restoration Theory
Explanation: Sleep provides ‘time out’ to help recover from daily activities that use up our physical and mental resources.
Muscle detoxification
Helps ward off illness
Growth hormone secretion
NREM is important for restoring and repairing the body
REM is important for brain development, higher mental functions such as learning & memory and neural connections.
Evolutionary Theory:
Explanation: Sleep evolved to enhance survival by protecting an organism by making it inactive during the most dangerous part of the day.
Amount of sleep needed depends on how easy it is to find food.
Humans sleep at night because we are visual, so we need to light to do a lot of our ‘everday’ things.
Our sleep may be a carryover from when night was more dangerous.
