6. Sleep Flashcards
Define sleep
A circadian state characterised by partial or total suspension of consciousness, voluntary muscle inhibition, and relative insensitivity to stimulation.
Why did early humans become motivated to sleep during the night
Evolutionary theory
There was a greater risk of injury while looking for food and drink when it was dark, as well as risk of predators that would threaten survival. Sleeping allowed for energy to be conserved.
Hunting and seeking water are better carried out in the daytime.
Impact of transition from sleeping on trees to on the ground
Evolutionary theory
Allowed for deeper and longer sleep. Scientists believe this improved sleep quality, led to enhanced brain function, and less sleep time required.
Meaning there was more time for learning and socialising.
Restorative theory of sleep
Restorative theory of sleep claims that sleep allows humans to recharge their bodies, to grow, and recover from the physical and psychological work encountered during the day.
Specific processes that occur during sleep
Restorative theory of sleep
- Cells resupply and stock up energy levels.
- Heal injuries.
- Reorganising and categorising memories and learned information.
Criticisms of restorative theory
- Assumes more sleep is required when physically active.
- Assumes body rests during sleep when brain is active.
Sleep-wake cycle
The reoccurring pattern of wakefulness and sleep that individuals undergo daily.
Melatonin
Sleep-wake cycle
The hormone that regulates the sleep wake cycle.
Circadian rhythm
The bodily cycle that lasts around 24 hours and controls the nocturnal release of hormones including melatonin.
Number and duration of sleep cycles
Sleep-wake cycle
4-6 sleep cycles with each cycle lasting about 90 minutes.
NREM stage 1
Description, duration, eyes, and muscles
Transitional period between wakefulness and sleep. Lasts 5-10 minutes. Eyes are closed but easy to wake, slow rolling movement until asleep. Muscles begin to relax.
NREM stage 2
Description, duration, eyes, muscles, body temperature, and heart rate
Light sleep. Lasts 20-25 minutes the first cycle, increasing with each repetition. Eye movement stops. Muscles continue to relax with occaisional twitches. Body temperature drops. Heart rate slows.
NREM stage 3
Description, duration, eyes, muscles, body temperature, and heart rate
Deep sleep stage, harder to rouse, disoriented if woken. Lasts 20-40 minutes for the first few cycles, decreasing later. Minimal eye movement. Muscles are most relaxed. Body temperature and heart rate decrease.
What happens in NREM stage 3
During this stage the body repairs and regrows tissues, builds bone and muscle, and strengthens the immune system.
REM
Description, duration, eyes, muscles, body temperature, and heart rate
More active brain, dreams. Lasts 10-60 minutes, increasing with each repetition. Eyes move rapidly in many directions, don’t send any visual information. Muscles temporarily paralysed. Heart rate may match awake rate.
Significance of REM sleep in regards to mood and memory
Dreams, which mostly occur during REM, may be involved in processing emotions. Brain processes learned information and motor skills from the day, committing some to memory and deleting some.
Wakefulness preparation in REM stage
CNS activates, which may assist in waking up. May explain why we spend more time in REM as the night progresses and why we wake easily during this stage.
Define sleep deprivation
The condition of getting inadequate quantity or quality of sleep.
Shift work
Causes of sleep deprivation
Night shift work disrupts natural circadian rhythms leading to challenges in aligning sleep-wake cycles with various melatonin, adrenaline, and cortisol levels.
Sleeping during the day can be interrupted by environmental factors such as light and noise.
Drugs
Causes of sleep deprivation
- Stimulants can hinder sleep by stimulating CNS.
- Alcohol is a depressant which can disrupt sleep once it wears off, causing people to wake up.
- Certain prescribed medicines can induce insomnia or impact sleep stage progression.