Chapter 4 Summary
is defined as a person’s awareness of the world around him or her.
defined as the state of awareness where our thoughts and feelings are clear and organized.
Altered states of
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
, 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.
, or loss of sleep, results in an increase in
, 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.
suggests that we sleep to avoid predators, while the
states that sleep is needed to replenish chemicals and repair cellular damage.
Both theories are probably
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
Non-REM sleep is a deep, restful sleep and consists of
Stage 1 sleep is also called light sleep and occurs when brain activity begins to shift from
Many people experience a hypnic jerk
in this stage when their body jerks suddenly and wakes
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
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
person is wakened from this type of sleep they often report being in a dream state.
Most likely, around 90 percent of