Chapter 4 Summary - Chapter 4 Summary Consciousness is...

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Chapter 4 Summary Consciousness is defined as a person’s awareness of the world around him or her. Waking consciousness is defined as the state of awareness where our thoughts and feelings are clear and organized. Altered states of consciousness describe a shift in the quality or pattern of a person’s awareness. Examples of altered states of consciousness include using drugs, daydreaming, being hypnotized, or simply sleeping. The sleep-wake cycle is a circadian rhythm , meaning one cycle takes about a day to complete. The cycle is regulated by the suprachiasmatic nucleus (SCN) located in the hypothalamus. The SCN responds to changes in daylight and regulates the release of melatonin from the pineal gland and body temperature accordingly. By the end of the day, higher melatonin levels and lower body temperature cause people to feel sleepy. In addition, high levels of serotonin are believed to produce feelings of sleepiness. The sleep-wake cycle tends to shift to a 25-hour cycle when subjects do not have access to the sun or clocks. Sleep deprivation , or loss of sleep, results in an increase in microsleeps , concentration problems, and an inability to perform simple tasks. Participants in a number of sleep deprivation studies reported that they were unaware of their impaired functioning. Two theories are currently proposed for why we sleep. The adaptive theory suggests that we sleep to avoid predators, while the restorative theory states that sleep is needed to replenish chemicals and repair cellular damage. Both theories are probably partially correct. Based on brain wave activity recorded with the use of an EEG, sleep has been divided into two different types, rapid eye movement (REM) sleep and non-REM sleep . Non-REM sleep is a deep, restful sleep and consists of four stages. Stage 1 sleep is also called light sleep and occurs when brain activity begins to shift from alpha to theta wave activity. Many people experience a hypnic jerk in this stage when their body jerks suddenly and wakes them up. As body temperature continues to drop and heart rate slows, sleep spindles begin to appear on the EEG recording, signaling Stage 2 of non-REM sleep. Stage 3 occurs when the slow, large delta waves first appear; and when delta waves account for more than 50 percent of the total brain activity, the person is said to be in Stage 4, the deepest stage of sleep. After a person cycles through Stages 1-4 and back, instead of entering Stage 1, people experience REM sleep. During this type of sleep, the brain is active and displays beta wave activity, the eye exhibits rapid movements, and the skeletal muscles of the body are temporarily paralyzed. This paralysis is referred to as REM paralysis . When a person is wakened from this type of sleep they often report being in a dream state. Most likely, around 90 percent of
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Chapter 4 Summary - Chapter 4 Summary Consciousness is...

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