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Chapter Final

PSYA01 Chapter 5 Exam Notes

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Steve Joordens

Psychological ScienceChapter 5 Consciousness51 Biological Rhythms of Consciousness Wakefulness and SleepConsciousness is a persons subjective awareness including thoughts perceptions experiences of the world and selfawarenessoWe go through many changes in consciousness every day as our thoughts and perceptions constantly adapt to new situationsCircadian rhythms are internally driven daily cycles of approximately 24 hours affecting physiological and behavioral processesoOrganisms have evolved biological rhythms that are neatly adapted to cycles in the environment For example bears hibernate in the winter Since this behavior occurs on a yearly basis it is part of a circannual rhythm meaning a yearly cycleoCircadian rhythms involve the tendency to be asleep or awake at specific times to feel hungrier during some parts of the day and even the ability to concentrate better at certain timesoLight is the primary stimulus regulating the human circadian rhythm Cells in the retina of the eye relays messages about environmental light levels to the suprachiasmatic nucleus SCN of the hypothalamus The SCN communicates signals to the pineal gland causing it to release the hormone melatonin which peaks in concentration at nighttime and is reduced during wakefulnessoCircadian rhythms change with age We need much less sleepespecially REM sleepas we get older People also tend to experience a change in when they prefer to sleepThe Stages of SleepoPolysomnography refers to a set of objective measurements used to examine physiological variables during sleepoSleep cycles are most often defined by the electroencephalogram EEGThese waves can be described by their frequencythe number of updown cycles every secondand their amplitudethe height and depth of the updown cycleBeta waveshighfrequency lowamplitude wavesare characteristics of wakefulness They are often interpreted as a sign that a person is alertAs the individual begins to shift into sleep the waves start to become slower larger and more predictable these alpha waves signal that a person may be daydreaming meditating or starting to fall asleep oThe EEG signals during sleep move through different stagesIn stage 1 brain waves slow down and become higher in amplitudethese are known as theta waves Breathing blood pressure and heart rate all decrease slightly as an individual begins to sleepAfter approximately 10 to 15 minutes the sleeper enters stage 2 during which brain waves continue to slow Stage 2 includes sleep spindles and K complexes which are periodic bursts of EEG activity The meaning of the bursts are not completely understood but evidence suggests they play a role in helping maintain a state of sleep and in the process of memory storage As stage 2 progresses we respond to fewer and fewer external stimuli such as lights and soundsApproximately 20 minutes later we enter stage 3 sleep in which brain waves continue to slow down and assume a new form called delta waves The process continues with the deepest stage of sleep stage 4 during which time the sleeper will be difficult to awakenAbout an hour after falling asleep we reach the end of our first stage 4 sleep phase then the sleep cycle goes in reverse and we move back toward stage 1 patterns We do not actually go back to stage 1 instead we move into a unique stage of REM sleepoREM sleep is a stage of sleep characterized by quickening brain waves inhibited body movement and rapid eye movements REMThis sleep is sometimes known as paradoxical sleep because the EEG waves appear to represent a state of wakefulness despite the fact that we remain asleepThe REM pattern is so distinct that the first four stages are known collectively as nonREM NREM sleep At the end of the first REM phase we cycle back toward deep sleep stages and back into REM sleep again every 90 to 100 minutesoDuring a typical night of sleep the deeper stages of sleep 3 and 4 predominate during the earlier portions of the sleep cycle but gradually give way to longer REM periodsoREM sleep appears to be critical to a good nights sleep When we are deprived of sleep we typically experience a phenomenon called REM reboundour brains spend an increased time in REMphase sleep when given the chanceTheories of SleepoThe restore and repair hypothesis is the idea that the body needs to restore energy levels and repair any wear and tear on the body from the days activities
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